and all of my mods were disabled

Try verifying your game cache - RMB it, click Properties, Local Files tab and then, find a big button saying VERIFY GAME CACHE...
Or, if that didn't helped, go to the same place, but instead click VIEW LOCAL FILES... button, go into 'garrysmod' folder, find folder 'downloads', go into it, and delete everything inside it, excluding folders 'models', 'materials' and 'sounds'. Or delete these folders too for more free space, though, you will have to download everything from servers again.

Re enable the firewall on windows

When i had that glitch i deleted my HL2 EP2 content pack so if youre using content packs then i would delete some and buy the game :/

hmm bad