This type of error will come when you are saving large application/Reloading the application bad memory is ther in Server. Work around is close the application and reopen.
if you are getting this message on the accesspoint, then you should be able to track it down in the QlikView Server logs.
And you can track the timestamp with the performance, in case you see that the server has restarted at the time you received the error message in the logs, then you might consider to add more memory to the machine.
I'm not working on Qlikview Server
This is an idea about my Local Machine:
Physical RAM(MB) 2730
Number of CPUs 4
CPU 0 Intel(R) Core(TM) i5-2400 CPU @ 3.10GHz 3093MHz
CPU 1 Intel(R) Core(TM) i5-2400 CPU @ 3.10GHz 3093MHz
CPU 2 Intel(R) Core(TM) i5-2400 CPU @ 3.10GHz 3093MHz
CPU 3 Intel(R) Core(TM) i5-2400 CPU @ 3.10GHz 3093MHz
this could be memory related,
I mean you a nice machine as a local machine with 4 CPUs and quite high clock 3.1 and you could easily increase the memory to 8 GB assuming that this is a 64 bit i5 core machine.