FIFA on laptop - HDMI output to an HDTV, drops in-game to a choppy 24 ghz

Hi,

I have just purchased an Acer Aspire 4820TG.
2.4 ghz
ATi Radeon HD 5650
4 GB Memory

Normally I play FIFA 11 on the laptop, and it meets the specs fine and everything, can easily play the top graphics on the display.
But I wish to connect it to my Panasonic HD TV via HDMI. When I connect it, the configuration displays the desktop and outside the game as 720p - 60 ghz which is great. However, when I load FIFA, the TV suddenly adjusts to 1080p - 24 ghz, and the game plays really choppy or even not at all in some cases.
I've tried playing it at the lowest graphic specs etc, lowest/different resolutions but no success. Is there any way I can play it on the TV at 60 ghz at all?

Thank you, help much appreciated!