Avast can't pass Firewall

Hi all…

I have a firewall in my network and each user need to access the internet must provide his/her username & password
but the problem with this approach is that avast! takes this as if it malicious behaviour … all i do is just stopping the on-access scanner and passing the required authentication and then back to activate the on-access scanner again.
Any logical solution?

Which is the message? Can you post a screenshot of it?

There is no message appears, but all talk is just my browser hanging when inserting user name & password and press submit button.

Im pretty sure ther is an option to exclude applications from scanning, when the message prompting for password etc. pops up try running taskmanager and find which process it is or try and get the applications name then add it to the exlusion list, only idea i can think of (not sure this will work but hey its worth a shot :P)