user login not working

some of our users seems not to be able to login to Zoho Projects. On the entry screen they input required information and hit enter, but the website just "hang up" (freezes with no reaction.

Deleting cookies does not help.

I read it is to do with some plugins in IE, however the only plugin the user has is Norton (antivirus or firewall???) and in my view this should not hinder logging in to a website.

It is a real nuissance and it might force our team to abbandon the whole zoho alltogether (which would be a shame!)

can anyone help?

Thanks!