RAW - JPEG Image Discrepancy

When I shot RAW+JPEG using my 20D with 24-70L lens, the difference between the pre-processed images looked about the same. Then yesterday, I shot RAW+JPEG using my 70-200L f/2.8 lens for the first time, and the pre-processed images were drastically different. The pre-processed RAW images, when I viewed using my Photoshop Elements 3.0, just came out looking good enough without having to go through any post-processing, whereas all JPEG images came out overexposed. I went out today for more shooting with the same lens and, again, all JPEGs came out highly overexposed. Why the discrepancy? I didn't touch the camera set up at all -- just default WB with both lenses. Then I was hit with the "Error" messages every few shots that drove me nuts. Don't know whether this has anything to do with the images coming out overexposed....

Any insights would be very much appreciated....

Does ACR in PSE3 have the "auto adjustment" boxes ticked? If so it's compensating for your overexposure automatically. Turn off the "auto" boxes to see it as it was shot. Not 100% sure of this because I use CS2 not PSE.

Thanks for the response, Tim, but there doesn't seem to be any boxes to set the auto adjustment in PSE3. Besides, I just double-checked to see whether the exact same problem occurs when using my 24-70, and the result is that the images shot with the 24-70 are perfectly normal -- JPEGs came out pretty much the same as the RAW images. So I'm befuddled as to why the drastic overexposure when using the 70-200? Since it only happens when using the 70-200 lens, it cannot be the PSE3.

I don't know any reason RAW/JPG should be significantly different. The lens you use should be irrelevant too. Are you using a flash, just out of interest?

No flash. Yesterday and today were both shot outdoors in sunny conditions. I'm getting kinda worried now since I had a bunch of "Error" messages while using the 70-200 today... like every 3rd shot...

You need to send your 70-200 in for repair, IMHO, and it might help to send the body too if you can spare it. Suck when that happens, once of my bodies is away right now.