VideoStudio :: Editing MOV Files From Canon 5D MKII?

I went from DV, to AVCHD earlier in the year. I had no luck at all getting one smooth render using AVCHD from my Panasonic camcorder. So when I bought my Canon 5D MKII I thought the HD files would be easier/better to work with. I have edited together some files just for tests with and without crossfades, but both have either resulted in shakey/jerky footage, or the program crashing saying 'send the dump file to Ulead for analysis.

Basically I perform smart proxy to shrink the files to make them smoother to edit, then when I try to render to .mov again, the footage is jerky, but then I can rerender to mpeg2. The problem is that the mpeg2 footage is only about 95% smooth. It will be flowing along then every 5-10 seconds there will be a jump. If I try to render straight to anything else - mpeg2, H.264, MPEG4, it just crashes after 3 seconds giving the same dump file message.

The files the camera produces are

1920x1080 quicktime (.mov)
25fps
48,000KHz, 16 bit, stereo

My hardware is

Sony Vaio laptop
Intel Duo Core 2.2ghz
Windows 7 home premium
64 bit
4GB Ram

Ulead version Pro X3

I have downloaded all the latest patches, and I downloaded the latest Directx (I'm not sure what this is, I just followed the link on the forum for the June 2010 one; is it an automatic thing?)

So I have a decent computer, and fantastic camera, and Ulead's top program - why can't I get a smooth end file??