Interlaced output problem

I'm having problems getting 1080i onto my tv(Mitsu 55807). MY HTPC consists of:

1800+

myhd 120

gf3 ti200 card

512mb ddr 2100

audigy soundcard

signal to tv through rgbhv breakout cable


I can get 1920x540p fine, but I can't seem to get 1920x1080i. I can't get it on my crt monitor either, but that may be the monitor limiting it, its only a 17inch. Any ideas on settings? I was using the default powerstrip 1080i settings. Thanks in advance for any help.