This has been a problem on my site for a while now (www.soulofmiami.org and to a lesser extent http://www.lifeisartfest.org). I did a search on the forums to see if I could find a resolution, but my search-fu is weak.
I've been using WP since July of 2008. I am by no means an expert, but I am pretty good. I am not an HTML or PHP hack, so I mostly just use the pre-made stuff.
Over the past few months, it has been getting worse and worse, where I often get "Page Not Found" or "500 Internal Server" errors while using the dashboard. This happens a lot when editing a post or page. Refreshing (F5) the page will eventually fix it, but nowadays it often takes 5 or more applications of refresh to get back to the dashboard.
I am hosting on Dreamhost using PHP 5.2 Fast CGI. I am using the Calatropsis Theme with the following Plugins
AddToAny: Share/Bookmark/Email Button
Contact Form 7
Contact Form to DB Extension
Facebook Share Statistics
Featured Tag Widget
Google XML Sitemaps
List category posts
Query Multiple Taxonomies
Simple Twitter Status Updates
Twitter Mentions as Comments
WP Render Blogroll Links
It is a very busy site, we have over 10,000 posts.
I have tried deactivating a few of the plugins here and there, but nothing rigorous. Does not seem to make a difference.
I have inquired with my host, and they claim it is a problem with WordPress or the plugins or something. Essentially, they said the issue is not on their end.
Does anyone else have a problem like this? Is this a known issue? Does anyone have any ideas on how to fix it?