Am using x50v with both 2003SE and WM5. Installed agilemessenger beta and it keeps on waking my device periodically. You wouldn't know if the device is on because the LCD is not displaying anything nor the backlight is lit!
I know it has been turned on because i have suspend my device while putting GSPlayer playing some MP3 in loop. I can hear the song playing as much as 30 times a day when it is in suspend mode! (the device will turn off by itself after 1 minute) This happens to both WM 2003SE and WM5.
So beware if you notice your battery drained overnight!
Took me more than 2 weeks to realise this.