I have a similar problem here. If I am running an OpenGL application (a game that I currently develop) and resize the OGL Window (this just reconfigures the Viewport and Projection Matrice), the whole box freezes. In addition, the keyboard led for caps lock and scroll lock are blinking - whatever this means.
I don't think this is a theading issue, and I don't think this is my mistake, since it works well on another linux box with an older nvidia driver and on Windows.
Athlon XP 1700+
SIS Chipset (was too lazy to look at which one)
3/4 GB DDR RAM,
GeForce IV TI4200 128 DDR
Debian/testing with 2.4.20 vanilla kernel
Current Nvidia Driver
I have not tried to downgrade the driver.