Incompletely creation of image-creations by imagecache

Hi,
I got different and strange creation of image-sizes by imagecache:

I have 3 presets:
1. portraet_einzel (scaling to 160x160, upscaling allowed)
2. portraet_liste (scaling to 72x72)
3. portraet_thumb (scaling to 56x56 and sharpen)

I want to work with the 3 sizes:
portraet_einzel provided by an imagefield and cck
portraet_liste provided by a view (image linked to node)
portraet_thumb provided by a view (image linked to node)

The following is confusing me:
1. portraet_einzel is shown
2. portraet_liste is shown on the block-view
3. portraet_thumb is not shown on the block-view!

I looked into the sites/default/files-directory and found this structure with the following contents:

1 file like portraet_einzel sized image

directory imagecache:
sub-directory potraet_einzel: empty
sub-directory potraet_liste: correct sized image
sub-directory potraet_thumb: empty (only imagecache_sample inside)

directory imagefield_default_images: empty

directory imagefield_thumbs: like portraet_liste sized image

directory images:
sub-directory temp: empty
1 other image file

directory js: empty

and some other files and directories...

What can I do? Please help.

I'm working with:
FileField 6.x-3.2
ImageAPI 6.x-1.6
ImageCache 6.x-2.0-beta10
ImageField 6.x-3.2
IMCE 6.x-1.3
Imce CCK Image 6.x-1.0-beta2