No TV Picture

[huggy_bizzle]

Firstly, I do hope I have entered this topic in the correct thread.

I recently purchased an Asus 550 ti graphics card after my old Asus 8800gtx died and I had to run everything off my onboard graphics. After installing the card last night and upgrading to the latest drivers I found that my TV (which acts as a second monitor) doesn't come on, it's a black screen and says 'no connection'. I am connecting the first monitor (a Samsung SyncMaster) via DVI and the Samsung 37" True HD TV via HDMI cable. This all used to work on my old graphics card albiet connecting th TV via DVI to VGA and also from the motherboard, when running from the onboard graphics via HDMI to HDMI. What am I doing wrong?
I have booted up the computer with the SynMaster disconnected to see if I could only run 1 screen at a time and still my TV shows no connection, I have correctly set up dual monitors in my Nvidia settings and it does detect my TV, I can even send my mouse cursor across and off my SynMaster desktop and over to what should be my TV screen. Do any of you guys know what i'm doing wrong?
Any advise would be greatly appreciated
Thank you in advance