As this is a UBB Threads site, the tuning recommendations made here are with UBB Threads in mind. You may find information more usefull to your needs on a vBulliten sight, as they would be tuning thier systems to run best for vBulliten.
That being said, and a disclaimer that all in all, I know jack about MySQL:
This looks like a problem to me and is where I would start: 26 zombie processes. That number seems way too high to me.