sitemap_index.xml.gz file seems corrupt

I think I have everything setup and it seems to be working, although I ended up just creating a symbolic link for the sitemap_index.xml.gz file from my docroot to the data directory.. but that seems to work now.
The problem I seem to have is that I am not able to gunzip the file once it is created. It tells me that the file is not in gzip format. I'm guessing that this file is just a gzip of all my forums xml files in the data directory, and that it should be gunzip - able. Where in the code are the xml files gzip'd I'm thinking that I might be able to make some modifications in the syntax to get the gzip to work properly?

Does Google recognize it as a valid sitemap file? If so, that's all that matters; that Google can open it. It's actually just an XML index that lists all the individual sitemaps. Example here:

http://www.fireblades.org/sitemap_index.xml.gz

You shouldn't need a symbolic link, however, since vBSEO's .htaccess file includes a rewrite rule to handle that.

I don't see the content of the file like I see in you link. The best I get with the sym link is a download prompt, if I select the "open with" gunzip I do see the contents of the file, and they look similar to yours. I'm not sure why it doesn't show the contents straight away...

So now I've removed the sym link and have the rewrite for the sitemap files in my .htaccess file, just like in the readme. And in doing that I now get a "Page not found". I believe my vb-root is correct because if I remove the rewrite lines from my .htaccess and copy the sitemap_index.xml.gz file to the vb-root I will get the "download" prompt... meaning it can see the file. Now I'm not sure how to get this working.

What is the current contents of your .htaccess?

RewriteEngine On

# Some servers require the Rewritebase directive to be
# enabled (remove '#' at the beginning to activate)
# Please note: when enabled, you must include the path
# to your root vB folder (i.e. RewriteBase /forums/)
#RewriteBase /

#RewriteCond %{HTTP_HOST} !^www\.yourdomain\.com
#RewriteRule (.*) http://www.yourdomain.com/forums/$1 [L,R=301]

RewriteCond %{QUERY_STRING} !vbseourl=
RewriteCond %{REQUEST_URI} !(admincp/|modcp/|chat|cron)
RewriteRule ^(.*\.php(/.*)?)$ vbseo.php?vbseourl=$1 [L,QSA]

RewriteCond %{REQUEST_FILENAME} !\.(jpg|gif)$
RewriteRule ^(archive/.*)$ vbseo.php?vbseourl=$1 [L,QSA]

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !^(admincp|modcp|clientscript|cpstyles|images)/
RewriteRule ^(.+)$ vbseo.php?vbseourl=$1 [L,QSA]

RewriteEngine On
RewriteRule ^((urllist|sitemap).*\.(xml|txt)(\.gz)?)$ vbseo_sitemap/vbseo_getsitemap.php?sitemap=$1 [L]

That doesn't appear to be the default vBSEO .htaccess. You have an extra RewriteEngine On line, which will cause problems. Try the .htaccess that came with vBSEO. It already contains the vBSEO Sitemap rules by default.

I changed my .htaccess file so that it only had the lines:

RewriteEngine On
RewriteRule ^((urllist|sitemap).*\.(xml|txt)(\.gz)?)$ vbseo_sitemap/vbseo_getsitemap.php?sitemap=$1 [L]

With that change I get a blank page in my browser. No Page not found.. I also get 404 errors on the other pages of my forums because I'm missing all of the other redirects.
I found no difference in having the extra "RewriteEngine On" in the file. Anyway I have put the other lines back in my .htaccess file, so I'm back to the Page not found error when I try to access the sitemap_index.xml.gz file.

No, use the one that came with vBSEO, not the one that came with vBSEO Sitemap. They are two different products, and the one included with vBSEO Sitemap is only for those people that are not using vBSEO already.

The default vBSEO .htaccess should look like this:

# Comment the following line (add '#' at the beginning)
# to disable mod_rewrite functions.
# Please note: you still need to disable the hack in
# the vBSEO control panel to stop url rewrites.
RewriteEngine On

# Some servers require the Rewritebase directive to be
# enabled (remove '#' at the beginning to activate)
# Please note: when enabled, you must include the path
# to your root vB folder (i.e. RewriteBase /forums/)
#RewriteBase /

#RewriteCond %{HTTP_HOST} !^www\.yourdomain\.com
#RewriteRule (.*) http://www.yourdomain.com/forums/$1 [L,R=301]

RewriteRule ^((urllist|sitemap_).*\.(xml|txt)(\.gz)?)$ vbseo_sitemap/vbseo_getsitemap.php?sitemap=$1 [L]

RewriteCond %{QUERY_STRING} !vbseourl=
RewriteCond %{REQUEST_URI} !(admincp/|modcp/|chat|cron)
RewriteRule ^(.*\.php(/.*)?)$ vbseo.php?vbseourl=$1 [L,QSA]

RewriteCond %{REQUEST_FILENAME} !\.(jpg|gif)$
RewriteRule ^(archive/.*)$ vbseo.php?vbseourl=$1 [L,QSA]

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !^(admincp|modcp|clientscript|cpstyles|images)/
RewriteRule ^(.+)$ vbseo.php?vbseourl=$1 [L,QSA]

Then, make sure your vbseo_sitemap/data directory and all the files in it are set to 777 permissions, and manually run the sitemap generator to create the first set of sitemaps. They will be updated each night with a scheduled task. Make sure you use the option on your vBSEO Sitemap menu to generate the sitemap, and not by manually running the scheduled task.

Once you do that, the URL to your sitemap should work: http://yourforumurl/sitemap_index.xml.gz

This was before I added the sitemap:

# Comment the following line (add '#' at the beginning)
# to disable mod_rewrite functions.
# Please note: you still need to disable the hack in
# the vBSEO control panel to stop url rewrites.
RewriteEngine On

# Some servers require the Rewritebase directive to be
# enabled (remove '#' at the beginning to activate)
# Please note: when enabled, you must include the path
# to your root vB folder (i.e. RewriteBase /forums/)
#RewriteBase /

#RewriteCond %{HTTP_HOST} !^www\.yourdomain\.com
#RewriteRule (.*) http://www.yourdomain.com/forums/$1 [L,R=301]

RewriteRule ^((urllist|sitemap).*\.(xml|txt)(\.gz)?)$ vbseo_sitemap/vbseo_getsitemap.php?sitemap=$1 [L]

RewriteCond %{QUERY_STRING} !vbseourl=
RewriteCond %{REQUEST_URI} !(admincp/|modcp/|chat|cron)
RewriteRule ^(.*\.php(/.*)?)$ vbseo.php?vbseourl=$1 [L,QSA]

RewriteCond %{REQUEST_FILENAME} !\.(jpg|gif)$
RewriteRule ^(archive/.*)$ vbseo.php?vbseourl=$1 [L,QSA]

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !^(admincp|modcp|clientscript|cpstyles|images)/
RewriteRule ^(.+)$ vbseo.php?vbseourl=$1 [L,QSA]


It behaves the same with this file.

Yes, that's it. You can see that the sitemap line is already included, so that part should be fine.

Now, did you generate the sitemap like I described above? And if so, check the vbseo_sitemap/data directory and see what, if any, sitemap_* files exist there.

OK, none of that made any difference, I still can't see the file. I checked my submission on Google and they can't see the file either. Guess I'll do some work around for now.