One of my clients landed themselves in this situation, by forgetting the service account password and then resetting it as an Admin.
QlikView Distribution Services was then totally unresponsive from there on in. Tasks would start and then not finish.
Reboots of the server and upgrade of QlikView Server (which was overdue anyway) didn't resolve the problem.
In the end the solution was to create a new Service user, apply this user to all the services and restart those services. Bit of a worry whilst the issue was happening though.
Note this issue has been raised here also: QlikView Server (QEMC) Publisher Reload not working
Hope this helps others facing this issue.
We had the similar problem in QMC most tasks were failing after QlikView service account's password change.
By looking closely to the problem failure was in distributing the documents to users and groups. So it was in AD lookup.
Resetting the Active Directory password in QMC/System/Directory Service Connectors resolved the issue.