Unable to logon to domain after installing norton internet security ?

After putting norton internet secutiry on 2 vista machines on my network i am now unable to log on…

I set up the trusted network etc. and was able to log on yesterday after a reboot

But today both machines are hangin on the welcome screen

I disconnected one of the machines from the network, re booted and logged on with no issues

Removed norton, connected network card and rebooted again and managed to log on first time

To prove i wasnt imagining things i put norton back on and rebooted and guess what

Im unable to log on again


Is there a setting i should modify to enable to me to log onto a windows domain ?