Yes there is a minor flaw in screen refresh.

Also if project is in panic mode, It will run an extra workunit.
eg.
Quad core + GPU
Normal = 1 GPU and 3 CPU
Panic mode = 1 GPU and 4 CPU

I've reported the screen redraw problem, others have seen it too. It has to do with the new way manager and client communicate which was a change in the last few clients.

As for running extra tasks, this is by design, See:
http://boinc.berkeley.edu/trac/wiki/GpuSched
Every one should get familiar with the new rules boinc operates under with co-processors.

What's happening is that the CPU jobs have earlier deadlines than the GPU job,
so BOINC runs them.
Then it gets to the GPU job and, because the GPU is idle, it runs it too.

I can duplicate this quite easily and it does on my (two CPUs and 1 GPU) run two CPU tasks in 'High Priority' mode and 1 CUDA=1/CPU task. I've got it doing that now. This is normal.