Just confirmed this by updating my Java to the latest 1.6 (I previously had 1.5 update 11).
Something must have changed within the past day, because suddenly I was getting an error that String.isEmpty does not exist. Some Googling told me that this method was added in 1.6+ versions and is not available in 1.5.
Just thought I'd let you guys (the devs, and anyone else experiencing this issue) know about it. Don't advise people to install Java version 1.5 anymore or they will encounter this error.