3.0.5 to 3.0.6 Update fail

I was attempted to update my board, it said update successful but then it went to the next screen and said it was checking files. Then it refreshed and said

"500 Internet Server Error"

The server encountered an unexpected condition which prevented it from fulfilling the request.
The script had an error or it did not produce any output. If there was an error, you should be able to see it in the error log.

I'm not sure where my error log is located, but that might help.

What should I do?