I'm using Jitsi 2.2.4603.9615 on Windows 8.
When Jitsi is running, it somehow stops other applications from starting
DDE (http://en.wikipedia.org/wiki/Dynamic_Data_Exchange) sessions.
As soon as I close Jitsi the DDE session can be established, and after that
Jitsi can be started, without breaking the DDE session.
Chrome had a similar issue a while ago:
Can this be logged as a bug?