20D not working right in creative modes

Hi all,

I've been learning alot here for a few months while I was trying to decide on a DSLR for which I owe everyone some thanks. I also just want to say that this is one of the most relaxed forums I've seen.
I have been using a rebel G , & Elph S200 but wanted something I could grow into. I eventually decided on a 20D w/17-85mm & 50mm f1.8 II, which I received at the beginning of December. I've been very happy with it and have seen improvement in my pics since.

Anyway, I need some feedback. The 20D now is only working properly in the basic modes. In the creative modes it just acts like I've set it to a 30 sec exposure when I shoot, but doesn't write anything to the card when the shutter closes. The top display reads normal. I can adjust the aperture & shutter speed, but that doesn't change what happens when I press the shutter. I've r&r'd the battery. The firmware is 1.1.0. I don't have the grip. I've reinstalled the firmware, I reformatted the CF card and tried a new one, & different Canon lenses. None of the above works. But as I said, it works fine in the basic mode including writing to the card. I've shot just over 1300 pics in the last month. I hope I just missed something, but I suspect that I will be sending it to Canon Canada to check out. I emailed them earlier today, but don't expect to hear back until at least tomorrow.

Any ideas would be appreciated.

Have you tried shooting raw and jpeg? So are you saying none (P, Av, Tv, M) are working? Have they ever worked?

Did you check your custom function C.Fn-12, to make sure that Mirror lockup is not enabled (C.Fn-12=1)?

Thanks for the quick replies.
I had it set to raw and jpeg. Also I usually shoot in Av & sometimes Tv with no problem until the other night. I checked mirror lockup and it was off. I think something happened the other night when I was shooting a couple of night shots outside. I took 4 long exposures, but when copied to the computer, only the first 2 were written to the card. The battery was low so I just thought that was it. But this morning I discovered the extent of the problem, & after I charged the battery. Boy am I confused.

OOPS. I thought I had reset all of the custom functions, & checked the mirror lockup. but I just checked again & it was on. Sorry for getting ahead of myself. I will be putting a post-it note on the back when using mirror lockup from now on. I appreciate the attempts to help though. I guess I should be reinstalling my firmware, not the cameras. Much thanks.