unable to start gmod ubuntu 16.04

[vic arpeggio]

Hi, I'm unable to start Gmod since the last update.

Thinkcentre M58p, 4gigs, Intel® Core™2 Duo CPU E8500 @ 3.16GHz × 2, Gallium 0.4 on NVA8.

I fished this out of the error log:

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ExecCommandLine: "'/home/vic2/.steam/ubuntu12_32/steam' 'steam://rungameid/4000'"
ExecSteamURL: "steam://rungameid/4000"
GameAction [AppID 4000, ActionID 6] : LaunchApp changed task to Starting with ""
GameAction [AppID 4000, ActionID 6] : LaunchApp changed task to SynchronizingCloud with ""
ExecSteamURL: "steam://rungameid/4000"
GameAction [AppID 4000, ActionID 6] : LaunchApp changed task to SiteLicenseSeatCheckout with ""
GameAction [AppID 4000, ActionID 6] : LaunchApp changed task to CreatingProcess with ""
GameAction [AppID 4000, ActionID 6] : LaunchApp waiting for user response to CreatingProcess ""
GameAction[AppID 4000, ActionID 6] : LaunchApp continues with user response "CreatingProcess"
Opted-in Controller Mask: 0
Game update: AppID 4000 "Garry's Mod", ProcID 783, IP 0.0.0.0:0
ERROR: ld.so: object '/home/vic2/.steam/ubuntu12_32/gameoverlayrenderer.so' from LD_PRELOAD cannot be preloaded (wrong ELF class: ELFCLASS32): ignored.
ERROR: ld.so: object '/home/vic2/.steam/ubuntu12_32/gameoverlayrenderer.so' from LD_PRELOAD cannot be preloaded (wrong ELF class: ELFCLASS32): ignored.
pid 786 != 785, skipping destruction (fork without exec?)
ERROR: ld.so: object '/home/vic2/.steam/ubuntu12_32/gameoverlayrenderer.so' from LD_PRELOAD cannot be preloaded (wrong ELF class: ELFCLASS32): ignored.
ERROR: ld.so: object '/home/vic2/.steam/ubuntu12_64/gameoverlayrenderer.so' from LD_PRELOAD cannot be preloaded (wrong ELF class: ELFCLASS64): ignored.
>>> Adding process 783 for game ID 4000
GameAction [AppID 4000, ActionID 6] : LaunchApp changed task to WaitingGameWindow with ""
>>> Adding process 784 for game ID 4000
>>> Adding process 785 for game ID 4000

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I tried updating to GLIBCXX 3.4.19 as per the blog post, afaik it's updated but still no gmod.

Works fine on Windows, and worked great on LInux until the last update. Any tips are greatly appreciated!

Thanks, vic