cant't switch from X to another VT then back to X

[mickfp <mickfp yahoo com>]

After a simple 'workstation' install of RH7.3 I can start X and it's fine. 
Then when I C-A-Fn to another (command line) virtual terminal that's ok too. 
But when I C-A-F7 back to X the screen is a mess. and I have to C-A-BS to 
restart X.

This happens on two entirely different systems.

Can anyone tell me how to fix this?