DNS Client Issues

Got a weird one that has me stumped in Windows Vista professional.

Environment.

Running 2 machines Vista pro x86
Running 1 machine Vita Ultimate x86
Running 1 machine Windows Home Server RC1
Running 1 machine Windows XP pro

Issue ONLY effects a single Vista Pro machine. I can see NO hardware or
software difference between this machine and another vista pro machine.

Issue.

Occasionally (for a period of several hours to several days every month or
so) am getting bad DNScache entries.

Searching ipconfig /displaydns shows "server failure of type A" under the
sites that are failing to load. Other sites are unaffected.

ipconfig /flushdns temp resolves this. The next time I open the site, it
works fine, but fairly quickly, the site is again unreachable due to the
DNScache being messed up.

Tried switching dns servers, but that made no difference.

Hope someone knows whats going on here, as its beyond me.

Am running with DNSclient service disabled for now, that stops all DNS
caching. but this is a BAD way to run.

Thanks

Natasha