Stuck on sending client

Always when i startup garrysmod for the first time after my pc reboots it keeps getting stuck on sending client. The balls are still spinning but nothing is happening, when i click cancel and try again it works. This isn’t really a problem for Gmod but in L4D1/2 it also gets stuck but i can’t cancel so i have to force the game to stop. But when i start it it keeps getting stuck again. So basicly i can’t play multiplayer anymore.

Does anyone know how to fix this?

Wich brand is your router?

How many addons do you have? How long do you wait? On my netbook gmod takes forever to load.