Anyone else kept disconnecting last night with a message of an invalid Steam ID?

That was really annoying

I did. It really was annoying, though luckily, I was able to instantly rejoin the Server and didn't have any problems for the remaining evening. It seemed to affect about two thirds of the people playing on that Server at this moment, so it's not an individual error.

I also got it two weeks ago during a Reg vs. Members fight. It was exactly the same problem and it was just as fast resolved. I'm hoping they'll fix this as soon as possible, though this bug doesn't really bother me that much.

I got disconneced alot then had no steam for the rest of the night

It's just something that happens occasionally. The authentification servers have a few problems and people playing Valves online games will get kicked en mass.