For some reason, my elderly NVidia 9600GT card refuses to work via a 7.5 metre HDMI cable to my newly-purchased Panasonic Plasma TV.  Yet it will quite happily do so over a 1.5 metre or 2 metre cable.  When connected via the 7.5 metre cable, the card doesn't even detect the presence of the TV, much less display any video to it.  Even at the lowest available resolution of 640x480/60Hz, nothing happens.

The 7.5 metre cable is brand-new, purchased from Dynamix and compatible with the HDMI V1.4 spec.  My Vu+ Duo satelliute receiver connects to the TV via this same cable with no issues at 1080i/50Hz.  Therefore, the cable isn't the problem.

Which video cards have people successfully used with long HDMI cables?

I am thinking of buying a GTX 650 as it seems to tick all the boxes that I need, without being overkill.  It has a full-sized HDMI connector (rather than Mini-HDMI) and has a large heatsink with equally large diameter fan, therefore should be quiet:

http://www.playtech.co.nz/afawcs0139235/CATID=762/ID=18797/SID=845461558/productdetails.html

From past experience, I prefer NVidia cards, but will look at ATI if there is some compelling reason.  It seems as though all recent cards support audio over HDMI, and this would certainly be nice to have.  The so-called "new generation" 610/620/630 cards seem to be rebadged versions using earlier chipsets, and may be little better than my existing 9600GT.  Therefore, either GT 640 or GTX 650 look like good choices for a PC which spends most of its time working standalone into a 27" monitor, and occasionally as a HTPC using BBC iPlayer or VLC Player to view content on my new TV.

If there are no Video Cards which will work via a 7.5 metre HDMI cable, I guess I will need to buy an HDMI extender of some sort.

Any and all suggestions/comments would be much appreciated.