My host just notified me of a similar problem with my board... I've opened a support ticket, but anything extra that can be suggested would be appreciated.
Small board, on a shared unix server, 2800 members, no code hacks, cp says 190K pageviews in March and 99.82% cache. Typical online folks range from 20 to 60.
Host is freaking out as server load is reaching 15% or higher and has disabled ultimatebb.cgi on me.
They want the problem "fixed" before reactivating... so? disable who's online, prune unactive members, what else?