Where did these WAVs come from? Do you know what bit rate and sampling rate they are recorded at?
I can't find anything indicating sampling rate (right click, Windows 7, properties)
Source = downloaded from free sound effects site.
Update - I opened my wav files in Audacity and found they were not good (although they worked in other players and MovieMaker). Problem resolved - I'll find other sound files to use.
Well, if you've got Audacity, you can make them good!
Just Export your file as a new WAV file. Audacity will output the new file with specs that Premiere Elements can work with!