blank pages to anything that has to do option

[gamora77]

Hello all.  Hoping for a little assistance.  I inherited this board and it is experiencing some troubles.  You can view the board and posts as a guest.  The moment you try and login or search, anything with "?action=****" causes blank pages.  They were running their own theme.  I reset it back to the classic theme.  I have scoured the majority of the blank page posts, but none of the solutions has helped.  Thank you in advance for any help you might be able to give.

Forum. 
santacruzguitarplayers.com/scgc-forum/index.php

Version
1.1.18

Don't know where to go looking for the error logs.

[Aleksi "Lex" Kilpinen]

Seems like a fairly highly modified and very outdated SMF, if SMF at all.

Are you able to access the forum admin control panel at all?
Do you have access to the server side logs?

EDIT:
At least the login and register functions seem to be Wordpress - not SMF.
Are you sure you are running an SMF install? ( If you are, you are also in breach of it's license. )