@ Justin
if you only got a portion of the show back into FCP4 then there is an error during XML parsing, this might be caused by incompatible filters or frame rate issues.
Try to remove the clip causing this error before exporting to XML - it's either the last one you see in the FCP4 project or that one which follows in the original timeline.
Sometimes you have to do several steps to get a project back to FCP4.
@ James
XML is just a (they call it human readable) description of a sequence or clip etc. This description contains only the path where the original media of every single clip is located - either as a file path URL or a reference to another clip.
So copying the original media into the folder with the XML, does make sense if you want to move the project to another machine, but the XML won't know about the new file locations. After you've opened the XML on another machine, every clip will be offline.
Regards
Andreas