WordPress MU

last night I made a new blog in my wmpu and started to post some notes. but, but and but (!) when the blog loads this error accures:

Not Found
Sorry, but you are looking for something that isn't here

I should mention this notes:

1-first I installed wpmu in the main domain, and later I moved it on a subdomain without any trouble, and everything was working great.

2- I installed a mu-plugin http://code.creativecommons.org/viewsvn/wordpressmu/trunk/mu-plugins/per_blog_registrations/perBlogRegistrations.php?revision=10338 to fix the signup problem in sub-blogs.

3- The previous blogs are healthy and work regularly. but new ones don't show their posts. but when I look at the database, the posts are there! and in the dashboard, I see (for example) the number of 3 published posts, but no posts are listed!

4- pages like "about" works. just posts have the problem.

5- I removed the plugin, but the problem still exists.

6- I made 4 blogs with different users, but all of them have the problem.

please help me solve this problem. Thanks in advanced.

I searched through the forum, but no answer!

I asked the server and mod_rewrite is on and they don't have any problem in reading .htaccess file.

Try disabling all plugins you have and see if it helps. If it does - enable them back one-by-one.

Check your server error logs.

Was this problem ever solved? It is happening to me now. I've got a few dozen teachers to train this afternoon and the issue just started.