Regular user unable to add remote printer

Hello, we have a strange problem on one of our Windows 2003 R2 SP2
printservers. For a couple of days our users get the following message when
they are trying to install a network printer on their workstation:

"A policy is in effect on your computer which prevents you from connecting
to this print queue. Please contact your system administrator."

This happens if the following are true:
- User is not a member of Power Users or Adminstrators,
- Printer driver is not already installed on the workstation.

The error does not occur when trying to install a printer from another
printserver (same os, sp level), or when the printer driver is already
installed on the workstation.
Exampe: user tries to install printer1, model hp laserjet 4 from the
problematic server. The error pops up and printer1 isn't installed. Then the
user tries to install printer2, model hp laserjet 4 from another server. That
printer installs fine and the driver is installed on the workstation. After
that the user tries to install printer1 from the problematic server again and
now it install fine too.

So it seems that something is preventing users from installing new printer
drivers from that particular server.

We have no printer policies through GPO's and the Domain Secury Policy has
this setting: Local Policies > Security Options > Devices: Prevent users from
installing printer drivers: Disabled.

I've tried restarting the Print Spooler service, but that doesn't resolve
the issue.

Thanks,
Michel