AVG IS INTERFERING WITH OPENING UP BOTH ROS online and offline

I am a practicing accountant and use the ROS (Revenue on Line) service quite a lot. I tried to download a new client tax form yesterday but it wouldn't download.  I immediately got on to the ROS Helpline (Normally on top of their game) but they said they couldn't help.  That it was something AVG had done and they were aware of the problem.  Suggested I try filling up the form online, saving it at each step of the way.  That worked up to a point but when the form was completed and I asked the computer to calculate it wouldn't and reverted back to the Start Page.  Can anybody help please ?