Vista - Lose Network in MCE mode

I have all my data files on one of my Vista Home Prem. PCs and my media files
are spread out evenly over 2 Vista Home Prem. PCs and the 1 Windows XP MCE
2005.

The problem is that the 2 Vista PCs start off seeing each other over my
network in Media Center Mode but after about 6 to 12 hrs the Vista PCs do not
see each other. When I take one of the Vista PCs out of media center mode the
other Vista PC can see it again.
It is important to note that all the other non Vista PCs on the network can
access data and media files at all times.

I have a home network setup with 2 Dell XPS 410 running Windows Vista Home
Prem. (Intel E6600, 4gig memory, 512meg video cards, and 2 Hauppauge tuners)
a Dell Dimension 9100 running Windows XP MCE 2005 (dual core Pentium 2.4, 4
gig memory,128 meg Ati video card, 1 Hauppauge tuner), 6 Laptop running
Windows XP, and 2 Work Stations running Windows XP.

Please help
Jon