[rin]

What I tried was to create a new plugin with hook "attachment_start" and with the simple line exit(). But still, the attachment would show up. I cleared the cache and it still showed up.

--------------- Added [DATE]1250506111[/DATE] at [TIME]1250506111[/TIME] ---------------

Got it working now.
Strange thing is, it will not exit the script when the thumb and attachment have been cached before?
Is there a better hook for this purpose than attachment_start?

--------------- Added [DATE]1250506751[/DATE] at [TIME]1250506751[/TIME] ---------------

It is very strange. On my test installation, it would work with 2 pictures, it would not work with another and it would show the path to the other instead of anything else.