I've tried disabling any other plugin that had been installed in the last few months. The most recent was an update to Joocial, a social media component and plug in, but I've since disabled all of it in an effort to fix this issue.

I'm running a very recent version of 2.7 DEV (two or three days old) - this was also a test to see if K2 was the issue, but it behaves the same as 2.6.9 did.

So Global Configuration's error reporting is not working and your error_log is not catching anything, right?

Without the error, we are in the dark. You should ask your hosting provider why 500 errors are not recorded in your error_logs.

Here is all I get from the error_log after clearing it and then forcing the error. I can't insert the log here because it thinks I'm uploading spam:

www.dropbox (dot) com/s/a7pz2wfztz7tkrv/error_log?dl=0

Thanks,
Kent