> i've re-installed drivers. i've tried different leads etc. i've checked
> the mixer input is set to line-in. i've physically removed the card and
put
> it back in.
This is a "duh" kind of question, but you haven't accidentally managed to
mute the input(s) in the control panel by any chance, maybe by running some
program that fiddled with these settings without asking you (it happens from
time to time; why? It's windows...

). You'll need to go to the Properties
window and switch over to recording mode to make sure all inputs are really
enabled.
If this does not solve your problem, go to soundforge's website and check
the faq, and then email their tech support before contacting creative,
because from what I hear they're hopeless and should only be tried as a
desperate last-ditch attempt.