'Page not found' for all my Google indexed pages!

All my Google indexed pages are in the forms of ../forums/6139-post2.html and if I click any of the indexed page I would get 'Page not found'.

Something must be wrong. I installed vBSEO 3.2 onto vBulletin 3.6.8 about a month ago!

Did you guys see this before?

Those are showpost links.

do you have showpost on?

~wrong post~

It was on before. But I turned it off a couple of weeks ago

which explains the 404s

So this is expected?

What's going to happen next? Will they eventually be converted to vBSEO URLs like /forums/xxx-xxx-xxx-1923.html?

It's pretty bad for someone to click a forum link and get 'Page not found'.

Correct, a 404 is a valid response, as the resource no longer exists.

The urls will not be converted to showthread as you described above.
They will simply eventually drop out of the index, and your other links will gain strength in the index.

Look at the member article forums, and find keith's article on building a custom 404.

Thanks. Is there a rule of thumb to say how long it will take before vBSEO effect kicks in?

It's been a month since the vBSEO installation and I haven't seen any change in terms of traffic from organic search engines.

In my Google Webmaster tool, I saw following. Is it normal? Only 354 out of 12598 got indexed. I installed sitemap generator a few weeks ago.

Sitemap stats
Total URLs: 12598
Indexed URLs: 354

it varies... and now that you're still changing things, its prolonging the effect.
If you never had showpost on, and had the sitemap generator installed from day 1, you would most likely be getting better SE results now.
The key is to get everything set up good and then leave it.
I've seen it take about a week to 2 months to fully start working.