This can sometimes be caused by QlikView running out of memory. Read up on optimising data sets and queries (you will find some articles on this on the Quick Intelligence blog) and ensure you have the statement written as simply as you can.
You could check Task Manager when the chart is rendering, which may point towards a memory leak.
If it is a particular expression then you could try building a new chart with the same expression - there could be something buggy going on - perhaps something lodged in the cache that is causing it to fall over.
Hope that helps,
This is not a bug. This can be caused due to Qlikview runnign out of memory.
You can check your expressions and try optimizing them.
Here are few threads from community which can help you or you can search the cmmunity for optimization or our of object memory:
Hope this helps!