Text input trouble on OS X Snow Leopard - text doesn't show up before mouse click

I have this strange problem on my MacBook Pro, running Mac OS X Snow Leopard. It comes and goes, but I haven't found out why or when.

The input cursor is displayed in a text field, e.g. the URL field in Chrome or Safari. When I type some text, nothing shows up. When I click with the mouse somewhere, the text that I typed shows up. If I continue to type, the same thing happens. Nothing shows up until I click the mouse.

There is another annoyance that I think is related. In a larger textbox, like the Xcode editor, the same thing happens, but when I click the mouse, it selects all text from where the input cursor is to where I click. Then it outputs the text that I typed, replacing what where selected.

If I click multiple times, it will always select all text from where I clicked to where I last clicked.

I have no good strategy for solving the problem. Sometimes switching between applications solves it, other times I need to close the affected application.

Have anyone experienced anything similar?

Is it possible that the mouse button is sticky or not clicking properly? This would mean that the cursor could be someplace on screen but the software is trying to follow mouse movements and expects you to click again where you want the text to go. We did have a mouse button on a MacBook Pro that just would not function properly, although the problem was different – you had to pound it to have it register. We ended up with a Bluetooth mouse that works brilliantly.