One of possible cause is when QlikView is installed on a 32-bits machine. On 32-bit QlikView use a limited RAM per process even though more physical memory may be available. Using a 64-bit could solve the issue.
If you have a 32-bit PC, you could play by checking which object is taking a lot “memory” or “CalTime” by
1. Making a backup of your application
2. Opening your application in QlikView Desktop >> go to Settings>> Document Properties >> Sheets tab and in the list of objects, look at “memory” or “CalTime” for each object
3. Remove some objects taking “memory” or/and “CalTime” and test again.
The issue could be related to complex expressions in chart object (use of complex IF condition, etc..)
Try to check the memory usage as well in Windows Task Manager>> Processes tab as you open your application and/or do some selections.
A recommended solution is to review use a 64-bit PC or try to review the model