Cubase 5 group channel panning problem

Hi, having a frustrating time with Cubase 5. Most of the time when I send panned tracks to a group channel they stay panned. every now and again though (particularly with vocal groups) when I pan the tracks and send them to the group, the left channel become centred and I lose the right channel completely.

The group track is stereo (routed to stereo out) and so are the audio tracks, and if I send the audio tracks to stereo out they pan just fine :confused:

Please help, thanks.