Internal Server Error. The server encountered an..

Getting this error message on browser.
" Internal Server Error

The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator, This email address is being protected from spambots. You need JavaScript enabled to view it. 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.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request."

before login it is fine. but after login when cart is empty and click on "shopping cart" menu link(checkout), I am getting this error. any idea? please help me.

Thanks,
Suranjit

One thing need to mention and find out. only one super user getting this error. other super or register user not getting any error. works fine. is this meaning anything?

I talked with server guys. they tell me below.

"Can you please contact the script support in this regard as there are no issues with the actual script, its just fine working for other users.

Also there are no issues with the server, so the script support may aware of such issues just in case. Please let us know what they are saying."

Thanks,
Suranjit.

the error is saying( hosting guy provided it):

HTTP 500 Premature end of script headers: index.php, referer: manaste.com/

is this will be helpful?

Thanks for your support.