WordPress MU

Hi.
I have a weird thing happening on my setup.
Everyone are allowed and can write comments and post them on memberblogs, but on the main blog, while everyone are allowed and can write comments, once they try to post their comments they get an error message saying "there's an error, please write a comment".

Any ideas?

Check your error logs.
Looks like problem with theme for me.

Solved it by removing the Yawasp spamfilter.
Replaced with another and tested ok by myself and an external visitor.