I'm testing out the Photo Mechanic demo but I don't get any EXIF info with RAW photos already on my system. However when I use Photo Mechanic to get the photos from my card reader I do get this info. I'm using a Canon EOS 300D. The Canon software gives me all EXIF info from any RAW photo file.
If you would like to send me one of the files that does not work properly, I'd be happy to investigate what is going on.
Have the older files been modified in any way? One thing to note is that there are standard EXIF tags, and there are Maker Notes which are camera/manufacturer specific which often duplicate the standard EXIF tags. It is entirely possible that there isn't much EXIF information left in the photos, and that the Canon software is showing you the values from their proprietary Maker Notes.
Either way, I'd be happy to take a look at one of your files. Contact me privately by clicking on my name to the left of this message. I'll give you instructions on how to upload to our server.
Thanks,
-Kirk