i've read some similar posts but none of the solutions have helped.
when i upload images and try to use them in the CMS all links are broken
and pointing to _resampled folder which does not exist:

[Sun Oct 26 18:49:09 2008] [error] [client 217.231.250.42] File does not exist: /home/wirt/site/assets/images/_resampled/StripThumbnail-silverstripe1.gif
[Sun Oct 26 18:51:10 2008] [error] [client 217.231.250.42] File does not exist: /home/wirt/site/assets/images/_resampled/ResizedImage10075-15minutes.gif

when i create the folder manually with 775 in every assets folder which contain
images nothing changes. only when i erase the width/height tags and the
_resampled/ResizedImagennn stuff with the HTML editor of the CMS the
images are shown and published correct.

im running php as cgi with rights of user/group of the complete tree of
the silverstripe installation - the rest of the system is running fine. this
image problem is the only trouble i have so far.

Yes created folder with 777 - no image is created in this folder but page references it.
I made another installation with running php as apache module. On this platform i
have not this issue - interesting is that it doesn't create _resampled folder and images
on this platform at all! It uses ?r=36034 appended to the image .gif url.

sizew.freakout.de - - [26/Oct/2008:21:02:13 +0100] "/home/tsselb/silvers/assets/images/15minutes.gif" "GET /assets/images/15minutes.gif?r=36034 HTTP/1.1" 200 5981

I can not see thumbnails on this platform - and have apache 404 for them in the log:

sizew.freakout.de - - [26/Oct/2008:21:01:58 +0100] "/home/tsselb/silvers/assets/images/_resampled" "GET /assets/images/_resampled/StripThumbnail-riscmon.jpg?r=32926 HTTP/1.1" 404 322

haha

As it turns out, gd wasn't enabled on the clients webserver. Oops...