Samba file sharing fails over Ad-Hoc WiFi, works over Ethernet

[JeffCGD]

I've run into a strange problem at work with our networking arrangement, which I hope someone can assist with.

Our marketing company has a art dept comprising 2 brand new Intel iMacs running Leopard 10.5.4, and one of our old PPC eMacs running Tiger 10.4.11. We have been mounting the Documents Folders of our Account Managers' PC's (2x Vista, 1x WinXP), so we can put artwork proofs into designated folders on their machines.

With our current floor plan, we have had to situate one of the iMacs away from any available ethernet jacks, so I have had the other iMac sharing it's ethernet connection over WiFi via an Ad-Hoc network. This works fine for everything EXCEPT connecting to SMB (Samba) shares, which simply fail when you attempt to connect. These work for the Ethernet connected iMac, and for EITHER iMac when connected via Ethernet, however.

Also of note: None of the Windows shares show up in the Shared section of the Finder sidebar of either Leopard machine, unless actually connected, whereas all available shares (Windows and Mac) show up as available on the Tiger machine, whether connected or not.

Networking is NOT my strong point, so if anyone knows what I'm doing wrong, please let me know.