lordy ... thats a hopeless format to be trying to edit and no mistake
try this:
1) download and use the free *MPEG Streamclip* application from
http://www.squared5.com/
2) open the app and drag your Camtasia clip onto it, then press *Cmd E*
3) change the
Compression popup menu to *DV/DVCPRO - NTSC* and then press *Make Movie* and save to your Desktop or other convenient location
4) now import that new clip into FCE and away you go
let us know how you get on