vSphere Client keeps refreshing

We are using an VMware ESXi 5.0.0 (Build 504890) and a vSphere Client 5.0.0 (Build 455964).

We can access the consoles of our VMs through the vSphere Client - however, approximately after about 5-10 mins the vSphere client seems to refresh and we are redirected back to the main vSphere page. We then need to reselect the VM and console.

Any ideas what could be causing this. Is there an update available?

Any help / links much appreciated.