(Note that VPOP3 v6.11 and later, the service startup system has changed so it should not suffer from this problem)
When VPOP3DB starts up, the service control manager component waits a set time for a response from the database server before it knows the service has started. If the PC is going slow (eg after a Windows update or if the PC is just slow) then this wait may not be long enough.
You can increase the timeout by following the steps below:
For instance, if VPOP3 is installed in C:\VPOP3, then the ImagePath setting may be changed to
c:/vpop3/pgsql/bin/pg_ctl.exe runservice -N "VPOP3DB" -D "c:/vpop3/pgsql/data" -w -t 1800