Steam Validation Rejected

I own the game legitimately on steam.
Launch Gmod, Try to join server, takes forever and then stalls on sending client info where I can press cancel.
After pressing cancel I try to rejoin that server and “Steam Validation Rejected”
I use to be able to join another server first then get steam validation rejected from that server and then join the server I actually wanted to join.
It takes me about 20 minutes to join a server then gmod usually crashes on joining if i get past sending client info.

Happens on other games, CSS and TF2, aswell.
Help would be very appreciated!

Link to your Steam profile. The one provided in your FP profile is invalid.

I had changed the custom steam url
I successfully joined a server but had lag spikes every 30 seconds or so.
I had a stable fps when suddenly frozen for a second and skips back and forth.

System Specs, Addons Installed (if any).

Sometimes this comes up with someone has spoofed your SteamID (I think). Restart Steam and it might go away.

I’ve restarted steam, reinstalled garrys mod, no change.

Intel® Pentium® 4 CPU 3.20GHz
3.0 GB DDR2 Ram
Microsoft Windows XP Professional Service Pack 3 (build 2600)
GeForce GT 220

Try deleting ClientRegistry.blob in /Steam/ then restart Steam.

After deleting clientregistry.blob I launched steam it updated and then I launched garrysmod.
I try to join a server and I get red text in the top right corner saying Disconnecting From Server.
I join another server and then I could play that one, I got a few lag spikes but I think theres something wrong with my CPU.
All was fine until my Client Timed Out.