There's some funkiness going on with the server - you may get the occasional HTTP 500 errors when commenting or doing searches. Not quite sure what's up but I don't think it is anything I can fix.
Update (4th July): The update is apparently caused by an issue with the latest version of the DBD::Mysql Perl module, used for allowing Perl applications like Movable Type to communicate with a MySQL database, and it particularly affects Cpanel installations like mine. Other MT blogs are having the same problems. As yet there's no word of a fix, though :( . If you get an internal server error, just go back and do what you did again, though please don't hammer the server.
Considering this also affects the MT backend interface, I guarantee you this is more annoying for me than it is for you.
Update (8th July): The problem should hopefully fix itself tonight when a fixed version of the Perl module is installed through cPanel's auto-update system. I've noticed that comments and trackbacks have been well down over the past couple of days despite the higher volume of posts and I'm guessing (hoping) that you're hitting the errors (and not just not bothering to comment).
No probs for me
You’ve probably already heard but, downgrading to DBI::Mysql 1.47 and DBD::Mysql 2.9006 should do the trick (it has for me!)
Arvind: Unfortunately I can’t do that myself (no shell access), only my host can.