We have users who have to repeatedly authenticate when opening IE which
has our local Intranet as homepage.

Some techs say they've had luck unistalling agents and clients and
reinstalling, but that can be very messy and it doesn't always seem to
work. I know I had it working that way, for awhile, but it stopped

XP Pro machines mostly, using 491sp1 and 65sp2. Not sure what they are
running on the servers.

I am blaming XPSP2 but any ideas on this?