You may find that it is easier to turn on PC file sharing on your Mac and make the mac available to the windows machine. Then work from the windows machine to copy the files where you want.
It is inconvenient, but I have found that it is easier to get working, since it doesn't require any special setup on the Windows machine.
If you don't need to access the files very often, this may be an acceptable work around for you.
I have never been able to reliably access the PC's folders from my mac. I can usually get to a point where I can see them, but I can't open them because of some type of permission issue...