I had the same issues when I tried to edit my Go-Pro footage using Powerdirector 8 on my PC,
I think it was down to Frame Rate in the end if it's been filmed in 30fps and edited at 25fps then it looks pants,
but since bought a mac and the difference is unbelievable,
Goodluck with it, Powerdirector 8 is't a bad program, but no comparison to final cut or Imovie's at that matter.
Cheers Rigger.....