I fixed it praise JESUS. I have 2 XP pcs and 1 vista. The fix was to install the xp hotfix on ALL xp computers. Then it works. I first did it with just one pc and vista could not see them on the network. Soon as I installed it on both and rebooted success.
Only explanation is if 1 xp pc does it not have LLTD installed it must block it from the others somehow. Please try this fix and I hope it works for you.
