[PD] GEM - nvidia GeForce 6150SE with nvidia proprietary driver and ubuntu 8.10 hangs for number of seconds

Running the nvidia proprietary driver, ubuntu 8.10 64 bit (Kernel 2.6.27-8) an open and rending Gem window will hang the machine for random periods of up to 30 seconds. Problem can be triggered by clicking and dragging the GEM window with the mouse and trying to move the window. CPU appears to be maxed out during that time. I tried NVIDIA graphics driver version 96 and 177 and the results were the same. If I switch to the open source nividia driver the problem disappears --- and I enjoy 75% CPU usage showing only a live feed to a Gem window on a 4G AMD 64bit dual core. ;-)

lspci describes my graphics card as an nVidia GeForce 6150SE nForce 430 (rev a2)

Besides using the open source driver, anybody know of a solution?