Win XP partition in Bootcamp dead after Mountain Lion upgrade

After upgrading my 3.1 Mac Pro to Mountain Lion, all my volumes show on the desktop

Bootcamp shows me the Windows disk choice....but after I choose it I get a black screen with the following error message

"Windows could not start because of a computer disk hardware configuration problem

Could not read from the selected boot disk. Check boot path and disk Hardware.

Please check the Windows documentation about hardware disk configuration and hardware reference manuals for additional information"

Anyone seen this? Any ideas? All was working well just before the upgrade. I never dreamed Mountain Lion would touch the WIndows partition, but evidently it did. Volumes on the desktop seem to be fine and have all files, programs and folders....just this boot error won't let me get to them

Thanks in advance for any help