I am running a QV9.0 SR3 webserver in combination with IIS, and have quite random service failures (once a day more or less).
The strange thing is, that in the Qlikview Enterprise Management Console (tab Status-->Services) the QVS service is perceived as down (only the QVS@domain service). When opening the Windows Services manager, and searching for Qlikview Server, the service seems to be running.
A restart of the Qlikview Server in the Windows manager however, does lead to the service coming back up (also in QEMC).
AW:QVS Service down in QEMC, not in Windows Services
Can you check the Event log (C:\ProgramData\QlikTech\QVS) and see if you have any entries that read: "Server aborted trying to recover by restart. Reason for restart: Internal inconsistency, type D, detected"?