Problems with Mac talking to Win7

I have a pretty strange issue. I have a home network with 3 windows computers, and 1 MacBook Pro (Feb11).

All the computers can ping each other in any combination/direction except the Mac can't ping the Win7 computer. (I have 2 XP, 1 Win7, and OSX10.6).

I turned the firewall on the Win7 machine off, and still no luck. Eventually I went ahead and tried to mount the Win7 share on the Mac, and that worked. Then, once the share was mounted, I could ping it just fine (and connect with other network stuff that I was trying to originally).

If the harddrive goes to sleep, the share unmounts, as normal, then when it wakes back up, the ability to ping etc, is gone again until I remount, then it's all back.

Basically: The Win7 machine can ping the Mac just fine, the workgroups are all set properly, and it can ping the IP of all my other machines, and other machines can ping the Win7. But the Mac can only ping the win7 if it has its share mounted.

Any ideas?

I tried both, but NETBIOS name didn't seem to work for the other computers if I recall, so just stuck to IP.

So, try to ping the IP, times out like crazy, mount the share, icmp comes back just fine.

Resolved

Just fixed the problem, ran windows update there were a couple items to be updated, come to find out I didn't have Service Pack 1 installed. I assume that was the culprit, since most MS products don't really work as intended until SP1.

Pings just fine now without having to mount.