I'm not sure exactly how I cause this bug but I've seen it twice now.
Works somewhat like this:
Click anywhere in the textarea and ensure there is whitespace before the cursor and nothing highlighted.
Click the link button
enter text, save it.
The link doesn't get added anywhere and now clicking the link button to create a new link has no effect.
I get JavaScript exception:
Uncaught Error: Offset could not be translated to a DOM element and offset: 6306
Version: unspecified
Severity: normal