I had something like that (only at server startup)one day when I removed an app from the server : it was Symantec AV for Domino (iSeries) and fortunatly I could see the console showing the "load appname (don’t remember the name) just before crashing. I just had to remove the task out of Notes.ini
This could be caused by a number of things and I would suggest you check a few basics first:
I would first start with the log and see what the last few instances were i.e. Had replication started, full text indexing started? Compact started?
You do mention that its hourly which would indicate some sort of task running every hour i.e. Replication / Connections etc that this error may be connected too.
Its really gonna be a process of elimination to find the issue.
Subject: RE: Domino crashes with PANIC: LookupHandle
It looks like there may be a problem with your event task. Have any new notifications been added to your events4.nsf database recently? Try stopping the Event monitor task to see if the server stabilizes. If it does, then run fixup, updall and compact on the Events4.nsf and restart the event task. If it crashes still, then it could be a bad document in the event4 database in which case, you would need to try and find the problem document(s). Hope this helps.