Black screen on install of Eden when connected to TV

My first installation of XBMC.
Specs AMD X2 240, ATI Radeon HD 4650.

Used Lili to put XBMCbuntu 11.0 on a USB.
Connected PC to <PC In> of 42" Panasonic(TH-L42S10) via VGA cable.
Plug in the USB and boot.
BIOS displays successfully on TV.
XBMC installation boot splash displays...
... then black screen.

At this point, I turn off the power and connect my PC to a CRT monitor via VGA cable.
I boot via USB, boot splash displays, and I can view the installation screen on the CRT.
I proceed with the installation on the CRT successfully,
XBMC works!

Now I connect my PC back to the TV and try booting into XBMC...
... same as before, I get a black screen after the boot splash.
If I switch to the CRT at this point, I see the welcome screen.
Then when I switch back to the TV, XBMC displays on the TV! but only at 1024x768 resolution =(


Any advice? I'm really quite new to all this, thanks =)