exchanga 2000 public folder error

I have a problem with my exchange 2000 server
free-buzy service. i get the folowing error at the event viewer: source:msexchangefbpulish
event id : 8207
Error updating public folder with free-busy information on virtual machine …. The error number is 0x8004010f.
dose anyone have an idea why this is hapaning?
the free-busy service cant update any free-busy info
thanks