I have an issue with my recent WP 2.5 installs. For the first day or so, everything works fine, including my theme and plugins, but after a couple days my Wordpress blog reverts back to the default them and all the posts are deleted and the original "hello world" post is recreated (I deleted this post when I install). In addition, all of my plugins are deactivated. I've been trying to resolve this in the WP support forums, but have yet to figure out what is causing this behavior.

Here's some info about my WP installs:
version 2.5
adsmindedwide theme
Plugins:
SEO All-in-One
Google Sitemap Generator
wp-cache

I was told by a WP support moderator that something is altering my database, since posts are stored locally. Is anyone else having this problem?

I installed via Fantastico. A moderator at WP support is fairly certain it's a problem with my database, hence my bringing the problem to lunarforums. I find it odd that nobody else here seems to be having this problem, which makes me think it could have something to do with the plugins I'm using (I really don't know much about how these scripts interact with the database and what changes they can make to it). I have done plenty of WP installs in the past using the same theme and earlier versions of WP. They are all still working fine. This problem is only showing up since WP 2.5, which unfortunately came out at the same time I started using these plugins, so it's hard to tell what is causing the problem.

Thanks for that tip. I've never used phpmyadmin before, could you tell me where to locate that (I assume somewhere on cPanel).

Have you tried to uninstall WordPress, install it again and see if the same issue happens?  If you could give that a shot, and it did the same exact thing - then that might be the issue.