Problems importing viosport helmet cam video to iMovie - 09 and HD

I'm having real trouble working with the movie files (.avi) from my viosport helmet camera. I have some qu.s as I am trying to put together a video this weekend (some background info is below - please help if you can!):

1. Has anyone worked with the viosport camera videos and edited them successfully?

2. They are labelled as .avi, but are not visible to iMovie 09 (ver 8.0.5). All my other .avi clips have no problem like this - are these videos actually a different format but cloaked as avi?! does this make sense?...

3. iMovie HD was importing them OK, but on some large videos (29min, 672MB) now comes up with an unknown error and fails to import - why? This file had previously imported without a problem.

4. NTSC/PAL - The videos were recorded in PAL, but iMovie HD only opens a new project as NTSC. The 'video format' options when opening a new project does not give the options that the help file says it will (there is no mention of PAL/NTSC next to the various options, only 'DV, DV Widescreen,...'). Can I change it once a project is opened - immediately or with videos imported?

Background:
The videos are saved in iPhoto and open in good quality in Quicktime, but are not visible to iMovie 09 and cannot be imported by any of the normal means that I have tried (file/import, drag and drop,...). I have no prob with my other video files. I have tried opening in HD and exporting as quicktime but the file size increases by many times if done at best quality. Doing this can enable '09 to see the file, but rather than 600MB it would become many Gb! - with lots of clips this is unfeasible to make a video (and even the 'best quality' is not as good as the original!).

This is my first real attempt at compiling a movie - any assistance will be hugely appreciated!

Partial success... NTSC changed to PAL

Ah ha! I watched this video:
YouTube - iMovie HD - Setting Up Proper Video Formats
It explained the difference (clearly) between NTSC and PAL. I changed the frame rate in preferences to 25fps and then opened a new project - the options still provided no choice between NTSC or PAL, but when it opened it was labelled as PAL.http://www.mac-forums.com/forums/mac_images/images/smilies/Smile.png

I have now started trying to import the previous file that failed unexpectedly... I'll post how it goes. I'm still really keen to hear if anyone has had experience with editing viosport videos.

Still no luck...

It didn't work :0( - came up with the same error. I've attached a grab screenshot.

All I can tell you is that AVI is NOT a format, it's a container, meaning your file could be using almost any combination of codecs.

See if it will work with MPEG Streamclip (free). If it does, you can easily convert it to DV (iMovie's favourite format) or MP4 (its second favourite).

Thanks chas_m - I am just trying MPEG streamclip after watching:
YouTube - How to import any movie file into Imovie

It worked!!!

chas_m was right, MPEG streamclip worked, although the 700MB went to 4Gb, but I don't plan to keep all the waste once I've made the video.

Another method that I'm trying is using FFMPEGX - see youtube tutorial: YouTube - How to convert movie files on a Mac).