most likely...
First, do a backup(because this is an educated guess), then:
I would try zipping them on PC, and then transferring them to the phone again, and then unzipping using phone's winzip or whatever(not the PC). Zip software retains the file creation date. Perhaps there is some difference between the two for metadata? This should work though as it will restore the metadata to be compatible with the phone's file system. I find it hard to believe that simply moving a file will cause the file creation date to be reset...but perhaps doing it via a usb connection causes something like this to occur. Moving the zip file back over to the phone will cause the zip file itself to change it's creation date, but not the photos themselves contained inside.
