[curt.clifton]

Strange. Were you typing into iChat? If so, is there any chance that you unknowingly hit the "Services → Send to Inbox" hot-key for OF? Or perhaps some hot-key configured in a launcher applications like Quicksilver or Butler?

Other far-out possibilities are iCal or cron. Any chance that you set up a repeating event in iCal with an "alarm" to launch OmniFocus?

You might want to email the support ninjas (choose Help → Send Feedback within OF). They've probably seen more ways that OF might be triggered and might provide other suggestions.

Good luck.