Upgrade to 5 and windows 7 can't access Mac on network

I've upgraded to Parallels 5 (build 5.0.9220) and have created a virtual machine with Windows 7

Two external disks that are connected to the Mac show up in windows explorer as mapped drives and are accessible but when I try to browse to them via the Mac on the network I get an error message saying that they're not accessible and "The endpoint is not valid"

Can anyone help please.

Thanks

Ruth