I've noticed an issue with PHP and the new WordPress installation. (2.5.1)
Submitting a 'blank' comment seems to throw a 500 Internal Server Error. This can also occur when WordPress is configured to check for email/name, and they aren't filled in correctly. Easiest way to reproduce is to submit a blank form as a comment.
Theme is irrelevant. No plugins need to be present.
This error is not specific to any installation I have. I created two new test installations as a proof-of-concept.
New Version (2.5.1) with the error:
Older version (2.3.2), no error:
The 500 error seems to occur in IE7.
Tested Firefox and the error does not come up.
I contacted the host to check to see if it was an issue there and recieved:
"This is something beyond our control .. servers are running the latest stable versions of php as released by DA. If it works in FF, but not in IE, it's not a server issue. I'd suggest posing your question to the wordpress support groups and see if they've got a patch in the works."