Figured it out -- changed the video decoder my computer was using for MPEG (ie, mpeg2 files captured by PP) to MainConcept by first finding out which decoder was being used (using GraphEdit:
http://www.digital-digest.com/dvd/downloads/showsoftware_graphedit_141.html...
and then bumping up MainConcept's merit value above that of the bad decoder, using DSFMgr :http://www.softella.com/dsfm/index.en.htm
Now AE properly imports the PP project file's vid clips, but now my prob is that it plays EXTREMELY slow (whereas PP plays fine...) So maybe I have to just bite it and export to QT lossless format from PP and take it from there...?