I updated the ScreenInformation class to stop caching the screen boundings. The caching caused issues when a saved dialog position is on an (now) invisible screen area (say when an second monitor/beamer is disconnected).
There was a note in the commit log from 2008 that there is a performance issue when obtaining the bounds on Windows. This perf issue only occurs on Java 5, and as we ship with Jitsi with a private JRE6 on Windows there is no longer an issue.
If you however notice a performance penalty under another OS, please drop me a message.