can't switch ttys after atp-get upgrade

["Tim" <debian@sp1r1t.de>]

hi everybody,

i've been using debian sarge on my thinkpad r51 for some weeks and
managed to get everthing to work. since i did an apt-get update and
apt-get upgrade yesterday, i cannot switch between the ttys anymore.

default runlevel is 5, gdm starts and everything looks good & works,
i can switch to another tty by pressing ALT+STRG+F1. once i do this,
there's no way back - neither to X11 nor to any other tty. the system
still works, so i guess something with the key mappings is broken but
i may be wrong.

of course, i did not switch the notebook on, upgrade it and shut it
down at once - but i don't remember doing anything that could cause
this.

did anybody experience similar problems or does anybody know a possible
solution? (would dmesg output be helpful? i guess not...)

tim