Using videos from Canon FS20 digital video camcorder in Final Cut Pro 6

Hi,
My question pertains to using video from a new Canon camera I got in FCP 6.

This camera is an HDD camera; it stores videos on its built-in memory and on a separate SanDisk Ultra II SDHC 16 GB memory card. The camera works great and takes great video, although it is not as compatible with my MacBook as I would like. The videos are in MPEG-2 format, and I am able to use this MPEG Streamclip program that I downloaded to convert the files to Quicktime Movies, which works just fine with FCP 6.

However, one problem I have run into is when I change the speed of one of these clips, say, like I take one clip and make it go 50% of its original speed, the video clip becomes very jumpy/shaky. The clips that are on normal speed look just fine, but the clips with the changed speeds become jumpy/shaky. I have tried as many of the video filters and effects as I can to combat this problem, but nothing has fixed the jumpiness as of now.

Any suggestions?

Also, as of now, I have to put the clips onto another non-Apple computer and then transfer them to my MacBook via external hard drive, because the software is not very compatible with Macs. Would a simple card reader that recognizes SDHC memory cards work to eliminate this extra step?

Thanks in advance for any suggestions.