CS4 Graphics accelerator works, but many filters don't work

I'm using CS4 with a Dell XPS 1710 notebook.
In preferences, performance, I set "enable OpenGL Drawing". It listed my graphics card "Nvidia Corporation GEForce 7900 GTX/PCI/SSE2"

I tried the rotation and zooming features and they worked well. As soon as I tried to apply a filter, such as 'filter gallery' or liquify, no preview image shows in the filter screen. It is just white. The controls work, showing I am zooming in, but no image"
Suggestions?

Are you on a normal layer? Is you image 8bit?

Hi John
I opened it this morning after a reboot and it seems to be working. Not sure why.
Now, getting a message "could not import clipboard because of a program error". Suggestions
thanks