The visual freezes!

Behrang's icon

Hi.

Running Max 5.1 on Windows 7 64 bit.

Around 10 minutes, I can't edit any patch anymore, the visual just freezes.
Impossible to get access to any drop down menu item from the patch window, nor from the main window.

I noticed that the only thing I can do is locking/unlocking the patch through the keyboard shortcut (Ctrl + E), and only the label "(unlocked)" appear/disappear ...

The amount of objects created is not the issue here, and there's no third party objects running, as I've been going through the basic MAX tutorials so far.