I was on Jay's server last night, and he too has no issue.
I really have no other idea on how to troubleshoot this right now except in suggesting you remove all non-default GMod addons except for ULib and ULX, clean out any extra gmod\data\lua\*\*.lua files that may be running on the server, then start adding things back in one or two at a time, testing the server after each time.
Yes, this is a pain, but the problem you're having only seems to affect a small percentage of people using ULib and ULX, especially in SVN.
From the "ulx debuginfo" command text.. the below are what addons I'm running on my development ded server.
Many addons are only maintained in SVN now, Wire (and it's models), PHX3, Adv Duplicator to name but a few.
If you're running those three, make sure you have thier latest SVN.
For now, test using ULib/ULX SVN.
Active addons on this server:
Adv Duplicator by TAD2020, version 1.8359 (July 5th 2007)
buildingblocks by om3ga, version 1 ()
counter-strike by Valve, version 1 (5th August 2006)
day-of-defeat by Valve, version 1 (22nd August 2006)
default_sent_pack by TEAM GARRY, version 1 (3rd December 2006)
derma by , version 0.1 (17th July 2007)
ForceField_Models by (null), version (null) ((null))
gm_mobenix_v2_hotfix by Sportkeks & MaZz3, version 2 (April 2008)
gm_skatepark_v2 by Towelie, version 2 (02/??/08)
hl2_ep2 by Valve, version 1 (29th October 2007)
masslessthrusters by JetBoom, version 1.1 (April 3st, 2008)
Material Ex by Jeffrey Carpenter, version 1.0.0 (16th April 2007)
phx3 by PhoeniX-Storms, 1/4 Life, hunter, joebloom, scragnog, x-quake, Xeon133, PelPix, version SVN (20th May 2008)
portal by Valve, version 1 (29th October 2007)
sui_scoreboard by Suicidal.Banana, version ? ()
tf2 by Valve, version 1 (29th October 2007)
TiledBlocks by hunter, version 0.5 (10th March 2008)
TRex by Xystus234 for programming & J-Dude for the animations. Some other guy made the models themselves, I forget who though., version 1 ((null))
ULib by Team Ulysses, version 2.2999 (00/00/00)
ulx by Team Ulysses, version 3.4 (00/00/00)
ULX_Explode by Mr.President, version 1 (4.2.08)
Umotd_Revived by JamminR - Team Ulysses, version SVN 2.A2 (04/00/08)
UPS by Megiddo (Team Ulysses), version 0.1 (00/00/00)
UTeam by spbogie, version 1.1 (03/25/07)
wire by Wire Team, version 0.9.6 (25st March 2007)
wire model pack 1 by Team Wire, version 0.3 (25st March 2007)
I personally don't need a list of your addons at this moment. I don't have the energy to go and test them all.
They may help someone else with the same problem compare the ones they have and go 'oh, we share these out of all..lets try removing those three first'