for all the people having decompression problems, instead of relying on the n900 to decompress the image, I instead decompressed it on a pc using 7zip. I too had the crash whilst decompressing.

Install steps I took:
- install the easy debian app from the application manager
- from your desktop computer, go to
http://qole.org/files/

and download either

debian-m5-v3d.img.ext2.lzma or debian-m5-v3e.img.ext2.lzma
depending if you want the v3e or v3d image

Open and extract this using 7zip.

Copy and then paste onto your n900 in the root directory.

Then just run the easydebian apps that you require (no need to do the deb img install)

Didnt see this posted elsewhere