We have been experiencing this weird problem oy n our network. The PC clients always suddenly disconnect themselves from the server. Mapped resources were all gone all of a sudden. When they restart their PCs and try to login, they will get "domain is not available or busy message". They can only logon after keying in the password repeatedly for 8 to 9 times, or restart their PCs a few times.
Not sure if there's any settings to tune on the SBS Server or PCs.