I don't seem to have this problem, but a fair bit of users on my forum have it. Whenever my friend tries to register, he gets this message:
I don't get this and I've tested this myself but 2 of my users already encountered it. I uploaded the .htaccess file without touching it, and then I tried adding "Options +FollowSymLinks" to try and fix the problem, but it didn't help.Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator, email@example.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.