Sitemap broken

I don't know why, but ever since I upgraded to Sitemap 2.1, my sitemap is broken and my google rankings are nonexistent.

Here's what I get when I click Your Google Sitemap Index URL: http://photocamel.com/forum/sitemap_index.xml.gz

Warning: fopen(/home/photocam/public_html/forum/vbseo_sitemap/data/downloads.dat) [function.fopen]: failed to open stream: Permission denied in /home/photocam/public_html/forum/vbseo_sitemap/vbseo_getsitemap.php on line 45

Warning: fwrite(): supplied argument is not a valid stream resource in /home/photocam/public_html/forum/vbseo_sitemap/vbseo_getsitemap.php on line 46

Warning: fclose(): supplied argument is not a valid stream resource in /home/photocam/public_html/forum/vbseo_sitemap/vbseo_getsitemap.php on line 47
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What a mess!

Can you help?

I've checked and double-checked the installation. Performed everything exactly as documented.

Hello,

make sure that you have 0666 permissions for data/downloads.dat file and 0777 for data/ folder.

Thanks. Works now.