I found the pattern (tho there may be more) that the BBCode parser seems to hate. Before I post it, I want to figure out a patch. :lol

I asked via PM the last person that caused the 100% CPU issue to edit their BBCode to remove the pattern from the post they were trying to make, and it worked without bringing down the server. No downtime since they made the change. :sun

I'm glad I finally found the issue, but I hope I figure out a patch soon. :rollin 

UPDATE: Pushed up a weak hotfix. Will keep digging.

I'll keep an eye on the downtime. If the 100% CPU issue is triggered again, I'll know how to find the post that caused it, and I can keep doing this until I've patched the most common causes. :lol