Windows 7 mapped drive screwed up

[ell]

Hi, I was just wondering if anybody found any issues with windows 7 and drive mapping to XP. I have a customer who I had about a month ago upgraded his vista machine to win 7. He had another pc with xp that we had mapped drives to for accessing/sharing data files for his appraisal program. Now it appears the drives are all screwed up, we get a error saying there is no access to the xp computer, I double checked it, its all shared ok, nothing changed. The xp machine is no longer visible to the win 7 one. I shut down the firewall and tried to re-map to it, no go, got a error message to check the router, and also a pop-up asking if I wanted to search the web for the files??? Both computers belong to mshome workgroup. The XP machine can access the win 7 no prob.