GW Messenger 1.0.6 on NW6.5 spk5.

We've only deployed messenger to a half dozen or so users. no problems for
about a month or so. Now I have 1 user that keeps getting booted
out...can't connect, or can't stay connected from 1 workstation. I tried
logging in as myself and had the same issue. Same user can log in from
another workstation with no problem. No other users reporting trouble. I
checked the TIDs, and the only mention of the client error "server not
responding" describes a more widespread version of these symptoms...i.e.
server-side corruption. but most everyone is getting along just fine.

Workstation is winxp spk2, nw client 4.91 spk2. double checked all the
network settings, and everything is as it should be. connected to a 1gig
switch. all other networking functions work fine...no firewall.

using edir authentication, but there is no replica on the server. GW 6.5
poa/mta running on the same box, client/server mode, with no problems.

Found errors on the messenger agent screen, so I set it to verbose, then
Diagnostic, and captured this when the user logs in:
verbose mode:

16:04:35 306 TCP *** PHYSICAL PORT DISCONNECTED, Tbl Entry=4, Socket=78
16:04:35 306 TCP *** NEW PHYS. CONNECTION, Tbl Entry=4, Socket=78
16:04:35 306 SPL Login: CN=user,OU=ou,O=ourcompany via 192.168.1.220
16:05:39 306 SPL Request (Create Conference) [0xD101]:
CN=user,OU=ou,O=ourcompany - Bad Parameter
16:06:04 306 TCP *** NEW PHYS. CONNECTION, Tbl Entry=5, Socket=79
16:06:04 306 TCP *** PHYSICAL PORT DISCONNECTED, Tbl Entry=5, Socket=79
16:06:04 306 TCP *** NEW PHYS. CONNECTION, Tbl Entry=5, Socket=79
16:06:37 306 TCP *** PHYSICAL PORT DISCONNECTED, Tbl Entry=5, Socket=79
16:06:41 306 TCP *** NEW PHYS. CONNECTION, Tbl Entry=5, Socket=79
16:06:41 306 TCP *** PHYSICAL PORT DISCONNECTED, Tbl Entry=5, Socket=79
16:06:41 306 TCP *** NEW PHYS. CONNECTION, Tbl Entry=5, Socket=79

set to "Diagnostic"

16:07:56 2E8 TCP Select returned OK
16:07:56 306 TCP *** NEW PHYS. CONNECTION, Tbl Entry=5, Socket=79
16:07:56 2E8 TCP Select returned OK
16:07:56 2E8 TCP Select returned OK
16:07:56 2E8 TCP Dispatched message for connection #5
16:08:29 306 SPL Login failed [0xD101]: m?ELY|-L-Lo-L-L - Bad
Parameter
16:08:29 2E8 TCP Select returned OK
16:08:29 2E8 TCP Select returned OK
16:08:29 2E8 TCP Dispatched message for connection #5
16:08:29 306 TCP *** PHYSICAL PORT DISCONNECTED, Tbl Entry=5, Socket=79

sometimes, it manages to log him in, then it bombs.
looks like the workstation is sending some kind of bad ju-ju or something.
I've tried several uninstall/reboot/reinstall to try to get it working, but
no luck so far.

Anyone got any ideas?