I experienced major problems when switching VTs on my pinstripe system,
involving X.

I have X 4.0.1 with the nv driver ( I have a TNT card ).

Example 1 :
Boot the system ( I have GNOME installed and run level 5 ) and wait
for the gdm login screen to appear. Switch to VT1, switch back to VT7.
The red hat logo in the background disappeared !

Example 2 : 
Switch to VT1 , log in as root and do "X :1".
You are now in an empty X screen on VT8. Switch to VT7
where a gdm login screen is ( you should not be logged in on VT7 ).
Notice how 99% of the gdm screen is gone ( replaced by that standard
black-and-white X background pattern ). The only parts left are the
picture of the GNOME logo ( the feet ) with the sign G-N-O-M-E under it
and the text filed for entering the user name.
Killing the server with ctrl-alt-backspace makes everything reappear
correctly.
Now switch to VT8. There should be the empty X screen , but it is entirely
black, with the mouse pointer being the only visible object.

This bug may be related to bugs 12611 and 15646