[SOLVED] disable_overscan=1 not working

[obo]

I've just installed a fresh XBian 1.0 alpha 4, with my TV connected over HDMI. The default config.sys appears to disable overscan, but I still have it present on boot. The Raspberry logo and kernel output are clipped, as is XBMC once it starts.

I've also been testing Rasbmc with a different SD card on the same setup, and it has no problem disabling overscan. If I remove the option I get a similar amount of clipped image to XBian.

I've not read any other reports of similar issues. I'm considering just copying the FAT partition contents from the working setup, but wasn't sure if the XBian files included specific settings.

Is there something simple I'm missing, or could try?