Scan on a scanner on the homegroup network

I have 2 systems on a homegroup network. On the Vista System is a printer/scanner. I can print on this from my Windows7 system but cannot scan - neither with the Paint program nor with Windows Fax and Scan. The scanner is not being recognized. I have the latest Win7 driver from Canon installed. I have even tried with the Canon Navigator 3.0. But that could not do it either.
I suspect some sharing problem. But since there is no setting for scanners, I am a little lost. Any ideas where to look?

Zidane, Hard wired works well. No problem there.

I already dropped a note to Canon. At least their Navigator should work - if it isn`t a sharing problem as I suspect.
And thanks for your help.

Here is the answer I got from Canon:

"Due to the hardware and software requirements for scanning, there is no
support for scanning over a network connection. We apologize for this
inconvenience."

I guess that settles this one.

Yeah, Canon says that it is possible on some models and not on others. This MP160 here was a freebie that came with the wife's laptop. I guess it falls into the second category. Will experiment with my IP560 that I have back home when I am there next summer. In the meantime I'll scan on the wife's laptop and use the result from a shared folder. No big deal.

Florida is always pleasant. I have my house here since 12 years and come each year from Nov. to May. Beats the weather in the Black Forest that time of the year. This year the say we'll have an El Ninjo year. That means more rain. But at least it is warm rain.