does not work with absolute path for tmp folder after upgrade

First thanks for this awesome work. I love to use this module!

I use imagecache with cck-imagefield, lightbox, views and taxonomy. Everything worked well, until I upgraded from 5.x-1.5 to 5.x-1.6. Now imagecache throws these errors on saving a new node:

• Location: http://www.example.com/sites/default/files/imagecache/kopfklein//var/www...
  Message: Source() not found.
• Location: http://www.example.com/sites/default/files/imagecache/kopfklein/sites/de...
  Message: Imagecache crop action ID 7 failed.

The crop action fails only for images I theme myself. This is what I have in node-mycontenttype.tpl.php:

print '<a href="/sites/default/files/imagecache/kopfgross/'.$field_rueckseite[0]['filepath'].'" rel="lightbox" title="'.$field_title[0]['view'].'">'.theme ('imagecache', 'kopfklein', $field_rueckseite[0]['filepath'], $alt = 'Kopfplatte', $title = $field_title[0]['view'], $attributes = NULL, $getsize = TRUE).'</a>';

Have a look at URL in the first error message. Looks like in this case imagecache expects the tmp folder (mine is /var/www/fastcgi/user/tmp/) inside drupal which it did not before.

The only other action I use is scale. This does work without problems.

Guido