Keep getting 500 Internal Server Error on VB 4.2.0

[Walt Gekko]

This has been particularly a problem the last few days:

For whatever reason, I've been constantly getting a "500 Internal Server Error" when I try to get to my message board (http://www.toosmarttofail.com/forums). It will let me log in at times, but even after running checks and the like and seemingly having the board working properly, the problem persists. I called my hosting provider, and it appears to be nothing on their end, while the rest of the site (http://www.toosmarttofail.com) is working properly. For example, on Sunday 6/24, after having problems with the message board, for two Price and Probability sheets we were offering FREE on the site, instead of having them go through the board as we normally do, we had them go directly to the sheets themselves for Churchill Downs and Woodbine (which had their Queen's Plate program on Sunday) as the rest of the site seems to be unaffected by this (I'm including links to the other pages to demonstrate that this seems to specifically be an issue with the message board where I am getting the server error). I'm even having trouble at times with the Admin page and logging in there with the same server error issue.

Any help to fix this would be appreciated.