So I noticed today, when I tried to go to system->configuration, all of the pages there were blank. I Google'd up some solutions and someone mentioned to go into user roles, click on the administrators, and hit save.
When I go into user roles, I lick on administrators, and it shows Server Error 500.
Can anyone give me some guidance on how to fix this issue?
Is this installation fresh? Or you just upgrade/downgrade your magento?
Please check this link, he also had 500 Internal Errors.
Credit to: @Aaron_bcn
If it can not fix, then go up to my answer to turn on Developer mode.