I'm having a strange issue. Here's some configuration info:

Exchange Server 2003 SP1 on Server 2003 SP1
Computers are running XP Pro SP2.

We just changed over a couple of our departments to use Outlook 2007
(previously were using Outlook 2000). Some of the computers have issues when
they open up Outlook 2007 where it will show as being disconnected from the
exchange server. Clicking on it and telling it to reconnect it will attempt
to reconnect and change back to Disconnected or Offline. So far to fix it
I've had to either reboot the machine..or if I close Outlook and go to
command prompt and do ipconfig /flushdns and then reopen Outlook it will
reconnect. It does this in both Cached Exchange Mode and non-cached mode so
it isn't that. All users having the problem are on our local network so it's
not a WAN or VPN situation. Also not all users have this issue at the same
time...one person it may work fine and someone else's it doesn't. At first I
thought it maybe tied to a problem with the DHCP/DNS leases, but people have
had it happen on consecutive days, not just on days their DHCP lease expires.
I have tried uninstalling and reinstalling Outlook with no luck and it has
happened both on older computers and brand new ones. This wasn't an issue
until changing from Outlook 2000 to Outlook 2007 on those machines and users
that still use Outlook 2000 continue to show no signs of this problem.

It really is an annoying issue because until they get it to show Online or
Connected they can't receive or send any new emails. Right now the handful of
people experiencing it I have created a batch file on their desktop with the
ipconfig /flushdns command for them to run themselves but am looking for a
permanent solution. Any ideas?