The date created metadata within the document is hosed, I've seen this with files in the past, not sure what causes it. Why that old date, who knows but it's a common issue:
Files/Folders with a Date Created of Dec 31, 19... | Apple Support Communities
http://forums.macrumors.com/showthread.php?t=502924
You'll have to use LR's Edit Capture Time command to fix it.