DNS Resolver Cache Error / Loosing Internet Connection

Running XP Home.

The computer with problem is connected to an MS MN-800 wireless router via
an eithernet cable. Connection will work fine for a few hours but the
computer suddenly looses the internet connection. Computers connected
wirelessly are not affected.

Repairing the connection returns a "Purging the DNS resolver cache" error.
I suspect this has something to do with the problem however I don't have a
clue how to address this error.

Changing users does not help. Cables have been checked and swapped with
other computers which does not help. Computer must be restarted to restore
connection then a few hours later the same thing happens.

The routers IP lease time is set for two weeks.

The computer's power settings are not set to turn off the NIC adapter.

Any clues regarding what may be going on will be appreciated
--
JJ