Some users can't open attachments in terminal server environment

Several days ago*, our terminal server decided not to allow some users
to open any attachments in Groupwise. Viewing works okay, and they can
"view in new window" and then do file/open from there to actually open
the attachment in its proper application. They miss the double-click to
open feature, though. For them, double-clicking doesn't do anything at
all. Right-clicking to "open" or "open with" also does nothing.

I see that some others have run into this with .pdf attachments; in this
case, it seems to be all attachments, but just for some users. If I log
in to the server as one of these users, I can't open attachments in any
GW mailbox. If I log in to the server as a user who's not having the
problem, I can open attachments in any GW mailbox. Although it
certainly seems like a Microsoft problem, I was hoping someone here had
solved it previously.

GW client 14.0.1
Server 2008

* Onset of the problem coincided with our migrating from a Netware to a
SLES server for files (but not for GW). If that's related, I'm missing
the "how." There have been no such glitches on workstations.