When using screen sharing (MacBook Pro w/monitor), I've run into two different problems. With Chrome, the Add-In tool wouldn't load, so I got no access to the Desktop at all. With FireFox and Safari, the tool loaded and gave me access. But then, it kept copying my desktop over and over like some awful, electronic echo. Anybody seen this before?
The screen recursion (endless copies of your screen) is usually the result of either a second instance of the meeting being open on the screen you are sharing, or your only instance of the meeting being open on the screen you are sharing and having the 'Preview Screen' feature enabled.
Either moving the meeting window to the non-shared monitor or minimizing the meeting window should resolve the recursion.
As to Chrome, Chrome shouldn't have an issue any more, but you can look at this KB article about why it didn't work in the past, Connect 9 Add-in support for Chrome browser.