Notes/Domino 4 and 5 Forum

Every several weeks, the user report no respond to server and we discover some 'abnormal' in the log. Here below:
-- log --
2005/11/01 03:56:17 PM ATTEMPT TO ACCESS DATABASE log.nsf by <dominoserver> was denied
2005/11/01 03:56:18 PM ATTEMPT TO ACCESS DATABASE catalog.nsf by <dominoserver> was denied
2005/11/01 03:56:18 PM ATTEMPT TO ACCESS DATABASE statrep.nsf by <dominoserver> was denied
2005/11/01 03:56:18 PM ATTEMPT TO ACCESS DATABASE admin4.nsf by <dominoserver> was denied
2005/11/01 03:56:22 PM ATTEMPT TO ACCESS DATABASE names.nsf by <dominoserver> was denied
2005/11/01 03:56:30 PM ATTEMPT TO ACCESS DATABASE events4.nsf by <dominoserver> was denied
2005/11/01 03:56:31 PM ATTEMPT TO ACCESS DATABASE doladmin.nsf by <dominoserver> was denied
-- log --
It seems not make sense, why the sever itself can't access it's own administration databases?!
Sometime we reboot the server but the user still can't access the domino? we have to wait and pray each time.