I've had that problem myself, it happens sometimes if you have auto-login when starting the computer, Steam cannot connect if the internet is a bit slow, so it gives an error message. This error message however likes to hide about on the computer, but it is easily fixed by simply going to the Task Manager (CTRL-ALT-Delete), going to the tab which says "Processes" and then closing down the Steam process, then restarting it. I It could also be a corrupt .dll file, I don't know which one is the exact one that usually causes these troubles, but I believe it's the vstdlib_s.dll. I know it's kinda late now, but yeah, I wouldn't recommend reinstalling Steam since you have to redownload every single game again (at least I had to) so it's really only effective to reinstall Steam if there doesn't seem to be any other way out.
