Why does it take so long to recover from a terminated program that had consumed all memory?

Every once in a while I run a certain program (MATLAB) and it takes up too much memory. At this stage the physical mem is at ~100% and the computer barely works.

I then terminate MATLAB and I can see the memory is freed on the task manager (image). However, it takes about 5-10 minutes until I have full control over my computer back. In these 10 minutes the computer gradually becomes usable, open programs get 'unfreezed', etc.

I guess that if MATLAB consumed all the memory then some other program's data was saved in the swap mem, but is it okay for this process of 'recovery' to take such a long time?

I'm using Windows 7 with intel i5-2500 and 12GB RAM.

Thank you.

(Why?)