Vista cannot access Windows 7 files

I have 2 Toshiba Satellites.
They were originally hooked via Linksys router. All was fine.
I decided to go wireless. Belkin router 802.11g, yeah, kinda old, but still works.
Windows 7 can access Vista with no problems at all. Files, printers, etc.
The Vista computer has a mapped drive Z: for backups to a USB drive on the 7 machine. Also I have files set to be shared as well on the 7 computer.
I hooked up the router, set up security, 7 computer is happy as a clam.
Vista, Device in use, Cannot access, permission issue.
I can ping the 7 computer with no errors. Just can't access the files.
I disabled the Windows firewall on the 7 computer, no luck. Installed Comodo Firewall, thinking perhaps it might see Vista computer and allow it access. Nope.
I have tried everything I can think of. Network Sharing Map shows the 7 computer, but again, just cannot access any files.
Anyone have any ideas?
I am at a total loss as to what the solution would be.
Internet access is working fine on both.
Thanks in advance for any help,
Herbie

Sorry, I should have told you about that.
Yes, same Workgroup. As I had mentioned before, this all worked when 'wired' and stopped working with 'wireless'. That is what is so confusing. I just don't get it.

Well folks, I have no idea what happened but it's working.
Only one comment, I removed the mapping to USB drive. Still didn't work. Then by chance I went over and lo and behold, network access.
Thanks for all your views and comments.
Herbie