If you didn't try this yet, try uninstalling and reinstalling all the content
I recall having something similar and fixing it with this back in LP
I found something that might work, well it worked for me so
go to options, multiplayer and set "allow all custom files from the server"
also don't alt tab when connecting to the server, works for me
Re-install the game?
Are you allowing Garry's Mod through your firewall?
lettuce know how reinstall works outYes its being allowed. I shall try to reinstall.
lettuce know how reinstall works out
turn off ur firewall and all anti-virus programs