253772 Quick diagnostic and fix job

My website has a member's area with several applications in there, including a forum, etc. All these are behind the site's username and password system. Some of these have decided to stop working. I've checked the directories and the files seem to be there, like index files etc., but the pages are coming up with a 500 error. I need someone to poke around behind the scenes, find out what's wrong and identify any security risks that may be glaringly obvious, etc. and get them working again so I don't lose any data. I'd prefer not to reinstall a backup if I can help it as I think this would just be plastering over the cracks rather than fixing the problem. As a side note, I also need a more permanent programmer for future upgrades and to be on hand for this kind of problem. The last long term programmer I had at the beginning of the year was really excellent, and he was from Scriptlance so I have no problem using someone from here on a more long term basis. So if you're cost effective, reliable, and interested in long term work starting early next year (just over 3 months from now), please let me know and I'll be happy to consider you for that too. Best Wishes Anthony