i have installed the XML ups module on my current website im working on, my server is running linux with php 5 and my sql 4, when a customer goes to check out which should bring them too the choose shipping method its hangs for about 2mins then brings up an error

"
Internal Server Error

The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator, [email protected] and inform them of the time the error occurred, and anything you might have done that may have caused the error.
More information about this error may be available in the server error log.
Apache/2.0.52 (CentOS) Server at www.legacytowelrails.com Port 80" Any ideas how to fix this error ?