If I'm reading things correctly:
Which Windows and Signlab version are you using there?
He didn't mention what version of Win he is running, but did say SL 10.
If that feature worked there and now stopped so you should check your Windows system.
It never worked
under SL 10, but it once did work under SL 8, but SL 8 won't open now.
Corruption in Windows system is perhaps likely, especially if there was an update recently.
It could have been a corruption of the twain.dll file that is used as an intermediary for WIA or the variable path could have been changed.
To my knowledge TWAIN support shipping with Windows stopped with ME (so it's been awhile and that makes sense, I haven't messed with TWAIN in a very very long time) and it's up to get it supported under WIA or have drivers shipped with the programs.
Corruption in the system could very well be where it is at.