This sometimes happened on my VM running Windows XP. Also I lost text/graphics using Refactor! Pro. If you are using a VM, try turning DX9 off in the VM settings and believe it or not, lowering the video card acceleration in the display properties. I can't use full acceleration in my Vmware virtual machines for some reason.
I think this also appears on client computers when the license is not compiled into the assembly, though I'd like Phil Wright to comment on that.