[seamusk]

ok, thanks for the info Tim. I think that it must be the sync services that is the problem. But you say not to touch that directory. So what should I do? It is clear to me after trying to run cleanup without first synching with iCal that the multiplication of todos is coming via sync services. Can I delete the omnifocus file there somehow?

I believe that I may have solved this issue by clearing the sync history in iSync. I'll know for sure soon.