Singleplayer not starting;Some servers are laggy

Actually, I have two problems. First, singleplayer does not start. I hit the start button, gets to “Establishing connection”. Frozen. I have to ALT-Tab outta the game after that. Second, is really confusing. Some servers I join are smooth, sometimes over 100 fps. But, some servers are below 15 fps, and they could be running the same map, and gamemode as the smooth servers, and have very choppy framerates. I checked the pings, and their fine, I ask everyone on the server, they are running smooth. Any ideas?

I can relate to this first problem. I can’t start a singleplayer (not that I ever play singleplayer anyways) game after joining a multiplayer game in the same session of starting gmod. This may be a gmod-wide dilemma.