May be old versions of phx mixing (or other addons)
I had a spawn menu issue at one time with the same I think, either it crashed, or would just show a tiny portion of the list.
This was right after a Gmod update.
Everyone was saying 'delete all of the gmod folder and re-install clean"
I found a much simpler fix.
Unfortunately I forget the exact folder/steps I did.
Had something to do with gmod/spawnlists
Try this;
Shut your game down (presume you know that, stated for safety)
Remove _all_ but default addons. These are default;
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)
hl2_ep2 by Valve, version 1 (29th October 2007)
portal by Valve, version 1 (29th October 2007)
tf2 by Valve, version 1 (29th October 2007)
(though you shouldn't have to remove ULX/ULib if you have it on your client game, wouldn't hurt either way)
Rename your gmod/settings/spawnlists folder oldspawnlist or something like that.
Now, once removed/backed up.. restart your game.
Spawn list should now work, albeit slowly.
In props, go to each category, let it rebuild the spawn list icons. Yes, this can take a while. It's still quicker than starting totally fresh again though.
Quit game.
Add phx back. I recommend latest if not SVN (I have no clue what latest release before SVN is)
Restart game.
Attempt spawn menu. Let it rebuild spawnlist for each icon.
Rinse, repeat for each addon that places items in spawnlist Q menu.
If that doesn't work, tell which point failed. That addon may be a problem.