I just changed servers and now two of my mod rewrite rules no longer work, but I have no idea why.
Do you have any idea why these rules wouldn't work?
RewriteRule ^u/(.*)$ /profile.php?u=$1 [QSA,L]RewriteRule ^c/(.*)$ /company.php?c=$1 [QSA,L]
Have you confirmed that mod_rewrite is enabled on the new server? AllowOverrides ALL? Have a look at my signature's tutorial for all that needs to be done on a server to enable mod_rewrite.
I'd normally ask whether you're using Apache but, since IIS is emulating mod_rewrite, that should not be a problem.