Smiley- Try plugging into a different USB port- uninstall and reinstall express scribe. That usually fixes the said issue.
Raghav- Are you running yours through a DB9 adapter to USB? Note that if you are running any serial port through an adapter NCH doesn't officially support that setup. It's almost a crap shoot as some adapters tend to work, some don't. If you are not using an adapter at all, I would suggest that you too, should uninstall Express Scribe and then reinstall it.