OK, so I solved it by myself.
Here’s the how & what I did:
opened up kramer.php
around line 966, changed
$_SERVER['HTTP_HOST'] . str_replace($_SERVER['DOCUMENT_ROOT'], '',
to
$_SERVER['HTTP_HOST'] . '/wp-content/plugins/kramer.php?kramer=gif-icon' . "\"
Apparently the DOCUMENT_ROOT-thing messed it up for my installation, resulting in the .comw:// in the post above.
So now I got the li’l K-icon working.
A word of warning: I haven’t had this running for very long yet, there just *might* be something that broke along my rewriting.