There are a lot of articles online about getting specific OS X and Windows versions to share nicely, so I'm sure you've already looked at one of those.
What I find most often when people ask the question here is that one or both of the machines has a software firewall turned on, or the software firewall is configured incorrectly. I'd check the respective settings on both boxes.
Hi,
yeah, i went on the net looking for answers; couldn't find a solution.
Firewalls are on on all Windows 7 and Vista PCs and accessing/sharing is fine.. except from Mac to those Windows vista/7 machines and vice versa.
Not sure if it helps, but this article is very comprehensive in terms of setting up the correct accounts and tweaking the shares on both platforms. I would recommend skimming it if you are convinced that the firewalls on all machines are tweaked properly...
File sharing between XP, Vista and OS X on a local network - PC & Desktop Computers