Sorry I was banned, sure I can help you.
Before you do anything I mention below, try starting a singleplayer game on any map and then from that game, joining the server.
You may also want to go to your options menu, the last tab, and then make sure "Download all Custom Files from Server" is selected. If it is and it's still not working, try to change it to, "Don't download custom files from server."
I'm going to need the following information from you:
- If you're using an autoexec.cfg, please post the contents of it in a reply.
- What launch options are you using?
- Does this only happen on a specific server or any multiplayer server you try to join?
- Have you had any other internet/connectivity issues?
Personally I did this when I was plagued by this curse,
BUT DON'T DO THIS UNLESS YOU WANT TOO, MAY BE A CVAR/LAUNCH OPTION
- Delete the steamapps/common/garrysmod folder.
- Right-Click Garry's Mod in your Steam Library, and hit "Delete Local Content"
- Unsubscribe from addons you don't need. Personally I just did a clean sweep and reinstalled the content packs I needed.
- Reinstall, mount your HL2/CSS/EP1/EP2.
- Let shit install.
- Profit.