After the upgrade of vCenter Operations 5.0.3 (vAPP) to vCenter Operations 5.6 I got an empty screen when I started the vCenter Operations Manager website and the Dashboard view:
So I started to troubleshoot and a Goolge search. When I found the following thread on the VMware communities: http://communities.vmware.com/message/2158059. The fix is really easy. Just clear your browser cache and after that, the Dashboard view will work again.