Interlaced output when rendered MPEG-2 in Vegas8
 

I have done many DVD's in Vegas and I always rendered to MPEG-2 then burn the DVD in DVDA and never had any problem, but now the footage looks so bad and the video looks so interlace.
My project setting is 1080-60i,
I have never change my setting on my project or on my render out.
I don't know what changed ? I tried every setting, the only good output is if I render to an AVI file and Interleave every seconds and every frame.
Any idea what am I doing wrong !!!!!