500 Internal Server Error When installing joomla extensions

[eat_good23]

I am trying to install the extension "Joomla Mobile" but whenever i try to install it from an upload or from a dircttory I always get an 500 internal server error. "The server encountered an internal error or misconfiguration and was unable to complete your request." Googling this problem leads me to many un answered threads on the joomla forums. Supposedly it has something to do with the amount of time scripts can run. Can this time be extended? another fix is also getting an admin to rebuild the .htaccess file. I am running joomla 1.5 . thanks in advanced.

[masshuu]

generally a 500 internal error is due to bad lines in an .htaccess file or a file/folder set to 666/777. We can't extend the execution time. Otherwise you can check or temporary disable the .htaccess file while installing and check that the files and folders have proper permissions.

[eat_good23]

I already Chmodded my directories to 775. Still getting 500. How do i disable .htaccess?
Thanks :P

[masshuu]

you can simply rename it to anything, like .htaccess_disabled