Insane connection lag after reformat

After reformatting my computer, every server I joined on Garry’s Mod had huge lag. Today I spent 5 hours on a server with my friend and had up to 10 minute lag spikes where I couldn’t move. Eg: I move forward and it jerks me back after 2 seconds.

Other problems include, job title not changing after selecting a new job (Dark RP) The screen ‘tumbling’ after lag spikes…

I doubt it’s necessary but here are my computer specs.

Dell XPS 420
Intel Core 2 Quad CPU Q6600 @ 2.40 GHz 2.39 GHz
NVidia Geforce 9800GT Graphics Card
Windows Vista

Strangely this lag is ONLY for Garry’s Mod, not Team Fortress 2, not Killing Floor, not Counter Strike Source or Etc.

Screenshots of netgraph3:

Help is appreciated.

Hmm, don’t know how to help sadly, but what server is that?

UKRP | Gang Wars. Very nice server that includes levels and unlockable jobs etc.