impress displays slideshow across half of two screens,

[mikeyp]

I just made the switch from Mandriva to Debian after some issues with a piece of software I was trying to run. Under Mandriva, I was able to use Xinerama to spread the desktop across both screens while keeping the panel on just the one. Impress meanwhile kept open the option to choose the display monitor and display on just the projector. Debian however, the option is greyed out, and running a presentation spreads it across half of each screen which is not exactly what I want.
Is there something I've missed or do I have to use it without xinerama? If so, is there a way of stopping the panel and icons loading on the second screen?
Thanks in advance.