Well, I figure that 9 exanodes is about 15,000,000 mhz of PIII power. This couldn't have been a problem with the stats box becuase they showed up at the team pproxy, and several of the dnet proxys are showing huge spikes as well.
I don't think this could be a trojan either. This is only a one-time dump. Unless there is a smart trojan that changes the e-mail addresses, or shuts down after a certain period of time, it wouldn't be possible to have a single huge spike like that.
The blocks also all come from one IP (right?). I guess someone could be hoarding trojaned (or real) blocks and finally flushed them. If they held for the entire 90 days or so that OGR 25 has been running, you would only need 166 1 ghz PIIIs, which is possible.
The last option is someone hacked the client so that it can submit bad results. I think this is the most likely scenario, but probably one of the hardest to clean up after.