I think I found a bug, and although I also found a workaround, here it is.
My environment: Windows 7, Photoshop CS5, Camera Raw 6.4 RC1, all of them 64-bits.
Steps to reproduce the bug:
1. Open several raw files at once in Camera Raw (in my case, Olympus E-PL2 ORF files, but it probably doesn`t matter). For this bug, take images that are likely to have different white balance settings. Also make sure that those are original files, never modified by Camera Raw (or anything else) and that they have no XMP sidecars yet.
2. Wait until thumbnails are generated (may not be relevant...). Don't click on any of them, just let them be created.
3. Click on "Select All". Again, don't change the displayed image, just select them all.
4. In Basic/White Balance, select Auto. All thumbnails are properly updated
5. Export settings to XMP (from the menu on the right-most toolbar, i.e. still "Basic" if you haven`t changed it)
6. Keep Camera Raw open, and have a look at the XMP files.
The BUG : they all contain the same white balance settings (crs:WhiteBalance, crs:Temperature and crs:Tint) which happen to be the computed settings for the first image (the only one displayed so far). All other settings seems to be fine though (i.e. they are from their respective image).
However, if you go back in Camera Raw and then click on some other images, not all of them. You can see that their WB settings are different and properly computed (as far as "Auto" can properly compute them). Export to XMP again. WB settings are then right, but only for the images that you clicked on. Those that were never displayed full size still have the wrong WB settings (from the first image).
Obviously, the workaround is to click on each of them. Still that's a bit awkward, especially in my "quite-automated" workflow, where I'm not yet to the point to look at each image individually. Can't tell if this bug exist too on any other version of CR, and my E-PL2 raw files can only be opened in CR 6.4 anyway (unless I change some tags to fool CR).
Can anybody can reproduce that bug on similar or different environment? And could Adobe fix it, if it is a bug?
btw, don't know why I wrote RC1... I just meant Release Candidate!