Probably the Flash settings are corrupt and for some reason Flash no longer communicates with the mic. You can test this by trying to hear a YouTube video or other Flash media. If that also fails to work, here is the cure for Windows computers:
1. Quit all browsers. For the settings clearing to work, no browser window can be open. Make sure to close the Adobe Connect window too, since that is part of the browser.
2. From the start button in the lower left corner, open the control panel.
3. Choose the Flash Control Panel. In the Advanced Tab, click Delete All button
4. Open your browser and try again.