Can't subscribe to site (EasyDiscuss)

One of our user has can't subscribe to the site in EasyDiscuss. When she clicks on the "site subscription" graphic, she gets a popup that says "You have already subscribed to discussions on the site. You may change the notification interval below:" When she clicks "subscribe" in that popup box, she gets "Your subscription is added successfully. Click here to review your email digest setting." However, the site subscriptions line always says "Site subscription is not active." The same thing happens if she clicks "subscribe via email" in the upper right.

I have logged on as this user on my PC and seen this behavior, even though it doesn't happen with my login using the same PC and the same web browser.