T1i/500D live view mirror going up and down?

I asked in the T1i/500D group but it seems like it got lost so I'm asking separately here.

Anyone with a T1i/500D tried live view and noticed that the mirror doesn't stay up? On mine at least the mirror goes down and then back up again on every shot. Is mine odd or is this how they work? With my 40D the mirror stays up the whole time while it takes the shot and only goes down if you use the 'fast' focus mode which uses the AF sensors so the mirror has to go down. Using mirror lock doesn't change anything, the mirror still goes down after the shot on my T1i. Anyone else? Same thing, different? I don't use live view much but I noticed the difference and wondered.

that's how mine works too, no clue why! haha

Snap, again not sure why, just thought this was the norm as it's my 1st dslr!

thanks guys, at least I know I'm not alone! Odd though.