There are several possibilies why qv services could stop. I my case it's happens when I haven't enough RAM available. But I think that also conflicts with windows-services caused problems. Have a look here for some hints to solve this problem:
Try clearing the Application log (Startup button, eventvwr, go to the Applications Log, right click, Clear Log). Another usual solution to this issue is to give the service that is failing permissions to log on as "Local System Account" (Startup button, services.msc, right click on the service, Properties, Logon Properties). If that works, you should change it to the QlikView account that is running all the other services and start it again.
Paul Rajesh suggested to change the port under web server to any thing other than 80(default) and try.
I couldn't find an actual reason/s for the services failure there.
I saw that the common solution was to write a windows batch scheduled task that restart the services once in a while.
That might be a solution to assure that all the documents are reloaded and the QVS is working properly but still, I'm trying to understand where I can find the failure reasons in order to prevent future failures. Both Windows and Qlikview log event viewers didn't really show a reason I could take care of...
It could be very difficult to find the reasons why the services failured/stop. First I think on not enough ressorces from RAM and CPU and the services remained in a kind of waiting after a timeout or similar - often they don't work for qv but for windows they runs.
For this you have to find the moment when the services stops (maybe if you looked from when are the last service-logs before you restarted the services) and search within the windows-eventlogs if you could find some correlations with the performance or another reasons access-conflicts with windows services on shadow copies or similar.