Odd windows service behavior

I have a windows service written in VB.Net. Periodically, the service
will seemingly just stop functioning even though it is started. A
simple stop and start of the service gets it going again. Is there
anything I should check for that would cause this? All the service
does is check for new files in a SAMBA folder and moves them to a
windows folder location. I have Try..Catch statements throughout the
service and no exception are being thrown. I even isolated the
service on a server with nothing else running on it and still the
issue pops up once a month.