Help, my 30D is acting funny.

I have never had this happen before, and it is really baffling me.
I put my camera in TV mode, and set my shutter to 1/250. I half press, and the camera changes the shutter speed to get a correct exposure! When I let go of the shutter release, it goes back to 1/250, and the aperture blinks to indicate it's too dark. In TV mode, the camera is not supposed to adjust the shutter speed right?

I thought I may be missing something, so I grabbed my 20D. I put it in TV mode, set it to 1/250, half press and sure enough the aperture goes wide open and blinks to indicate too dark, but the shutter speed does not change.

Can anybody shed some light on this for me?

Did you make sure that the on switch is lined up with the white line above "on"? I have made this mistake a few times in manual...

Yeah, that's one of the first things I checked. I also just pulled both batteries, even the small "watch" battery out. No luck, it still does the same thing.

Have you got safety shift on?

Your gonna have to help me with that one, where's safety shift?

I don't recall which custom function it is; check your manual or have a look through the list.

Ok, let me check it out.

Jim G, thank you! That was it. I don't remember ever changing that.

No worries

Though this is solved, the other thing that can cause Tv to shift is attaching an external flash, since you can set the shutter speed to always match the curtain speed. In your case this isn't it, but hopefully someone will be smart enough to use the search function and see it.