Ctrl+alt+Fn not showing consoles

[rudu <rudu@cegetel.net>]

Hi,
Running squeeze on AMD64 arch, my system recently stopped to let me get 
my consoles after I hit the ctrl+alt+Fn keys (n = 1 to 6).
Instead, my monitor first blackens then presents me the exact replica of 
my graphic session's screen except that it reacts to nothing, there is 
no mouse cursor anyway, until I hit ctrl+alt+F7 to get my fully 
functional graphic session back again.
I tried to replace gdm by kdm, to test from within KDE4 or gnome, and 
got the exact same behavior.
I don't know where to look now, nor which words would make a valuable 
google search ...

Thanks for any help.
Jean-Marc