I don't entirely understand your question.

Are you saying that files you check out on one machine seems to be unaccessible on another of your machines? I'd say that would be entirely by design, as now you have a file that has local modifications done on one machine, which may or may not be available on your other machines.

When you say checked out by somebody else, what does that mean exactly? How are you verifying this, what are you looking at?

Or do you mean something else? In that case, please elaborate.