i945GM retrieves 0x0 0Hz 0KHz modes from HDTV set

[Sixer]

Hi,

I have a Mac Mini (Intel) with an Intel 945GM chipset hooked up to an  
HDTV through a DVI--->HDMI cable.

I know the DVI-->HDMI connection works, I have tested this under OS X.

Now that I've switched to Ubuntu running Xorg 7.1.1, I cannot seem to  
get any display mode working. All the modes retrieved in the final  
part of Xorg.0.log read:

         ModeAttributes: 0x0
         WinAAttributes: 0x0
         WinBAttributes: 0x0
         WinGranularity: 0
         WinSize: 0
         WinASegment: 0x0
         WinBSegment: 0x0
         WinFuncPtr: 0x0
         BytesPerScanline: 0
         XResolution: 0
         YResolution: 0
	[...]

Finally resulting in:
(EE) I810(0): No Video BIOS modes for chosen depth.

I'm looking to override these modes and specify them, ignoring any  
detection through either DDC, EDID or VBE. I'll admit right now that  
I'm not sure which does what, but disabling DDC and EDID has made no  
difference. I've also tried to use the vesa driver instead of i810.

I have specified a couple of modelines:
         Modeline "1280x720"  74.48  1280 1336 1472 1664  720 721 724  
746  -HSync +Vsync
         Modeline "1920x540"  81.57  1920 1984 2176 2432  540 541 544  
559  -HSync +Vsync

My TV set, a JVC LT-26S60 LCD panel, is detected:
(II) I810(0): Size of device DFP (digital flat panel) is 1920 x 540

Both 720p (1280x720) and 1080i (1920x540) work under OS X, that is,  
by using a shareware app to specify those resolutions. Early at the  
boot stage also, presumably during loading the EFI, my TV briefly  
goes white (instead of blue/blank) and reports a 720p incoming  
signal. Upon booting Linux, it goes blank again.

My question is: How do I ignore whatever video modes my TV reports to  
Xorg, if any, and force 1280x720 at 60Hz or 1920x540 at 60Hz?

TIA.


Sixer