Blank Pages in Admin? HTTP Error 500 (Internal Server Error)

After I tried to install the multiple admin add-on my admin page went blank giving error 500. So after searching in the forum I found that in CPanel I can find why the error came.

The error was a file that was calling the same thing that was called in another core file. So I deleted it (plus I deleted the whole files that came with the multiple admin addon) and the login page for admin started working. And so the index of admin also is working.

But the problem is every single other pages in the admin area (orders, categories, extra pages, languages,...) they all give a blank page with this error :

HTTP Error 500 (Internal Server Error): An unexpected condition was encountered while the server was attempting to fulfil the request.

What shall I do? My cart is working fine, it is only the admin part that is not.

I think we are going to need a bit more info before we can answer your question. What shopping cart are you using? Do you have access to your error logs? The error you are getting is a generic error of which the details of what is causing the error usually gets logged in your error log file. Many times you will find a file called error_log somewhere in the same directory as the script throwing the error.

What sort of server are you on? Windows? Linux?