The driver can't respond to PAINT events, so it has problems with XFree86 v4 because the backing-store is not enabled by default. The best solution is to have a context to save the actual window (and the GrPixel problem can be solved too). The workaround is to add next lines to the /etc/X11/XF86Config-4 file, in the Device section:
Option "BackingStore"
Option "SaveUnders"
Hope this help