blocked emacs

[Nicolas Rist]

Sometimes emacs blocks. (more than 10 times/day)
I have tried to find out when it occures, but I can't find any common 
characteristic;  sometimes it is enough to type on the control taste.
In this case, the IO are blocked, except the scroll wheel of the mouse. I 
used Windows 2000, so with Alt-Tab I have access to others software, but 
the IO are still blocked. With C-A-del I can logout, and often it works, 
but sometimes I must reboot.
Any tip ?

                Nicolas

PS: emacs 21.3.1 for windows