Windows 7: 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

Are computers in the same 'workgroup'? What anti-virus programs are you running?

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