[Plugin: W3 Total Cache] Users can't login

Hi I installed this plugin with great success but there is now huge problem with page caching enabled. Users can’t login to the site. Is there a solution to this. It doesnt login with either firefox or IE. I tried once clearing my browser cache and could login but I cant tell the thousands of other users todo this. I tried to explain this to someone and they couldnt get it right. So this is a bit of a problem and Im forced to switch caching off for now 🙁