response.addCookie problem

Hi, 

We have an program that needs to be run by multiple users over our intra
net.  But I have met a problem with addCookie. It works fine on some user's
PCs but not on some others'.  Worst of all, it works fine some times not
other times on my own PC.  I have checked my IE settings and permission on
the cookie directories, everything seems correctly set.  

Any help would be much appreciated!
Thanks
Alicia