Sony Vegas 8 Movie Studio Platinum (newest update 8.d) can't import the .m2ts files from my Canon HF-10 camera. It just refuses to import the video ("unsuppported format").
First of all, there is no HF20 model from Canon. There's only HF10, HF11, HG20 and HG21.
Secondly, the AVCHD support was rewritten for Vegas Platinum 9. So I suggest you download the TRIAL of Platinum 9 to try it out if it works (it can get installed in parallel to 8.0d). If it does, then you need to upgrade.