problems with .htaccess file

Dear everyone!

I’m currently maintaning a site, with a rather bizarre structure. A new site was just created , http://sfu.dk. The old site has been moved to the domain http://meebox.sfu.dk, and is hosted on a completely other server. The redirection is done using gratisdns, a service similar to opendns. Now here is my problem:

Since i started just a few weeks ago, i encountered a “500 error” everytime i tried to go to “site.test.com”. I quickly figured that it was about the .htaccess file being corrupted, so i tried to rewrite it, and in the end, i just renamed it to “.htaccess_old”. After that the frontpage worked, but everytime i click on a link, i just get an 404-error.

I think that i need to rewrite the .htaccess for the new URL for the site, but how do i do that, when the .htaccess file in the first place is corrupt?

Best regards