1 - my timeline comprises titles, videos and JPEG pics and audio. Seemingly random JPEG pics "switch off" in as much as I can still see them in the library, and in miniature on the timeline, but when the clip is played (separately or in movie mode) the screen is blank for the pics duration. If I delete the pic from the timeline, and drop it back in, same thing, blank. And it has affected numerous pics. i have mixed luck in resolving this by deleting the pic from the media library and importing it again from the hard drive - sometimes it resolves, other times not.
2 also, I get exactly the same issue if I try to add magic (ie zoom) to a JPEG. As soon as I try to preview it, the pic goes black (or blank).
I'm using a Sony vaio 64bit with freshly updated Nvidia drives, 4gig ram, windows 7 Intel i3 2.3 ghz laptop.
This is the second movie I have made. The first one turned out great, but it was just movie clips, titles and audio (no JPEGS)
So...can't use zoom, and intermittently loosing visibility of my jpegs.

If you have experienced this and found a way around it, I'd love to hear. It could just be that the JPEGS which are about 2meg files, are just too big for my laptop to process.