It seems like I wasn’t that stupid after all:
Thanks to Eirikso for catching a mistake in the new install instructions for Bot-Check in WordPress 1.5. The old instructions have you remove an if statment that checks for a logged in user. A new download has been put up with correct install instructions.
Right before the line
Logged in as …
So, now I am up and running with the latest version of BotCheck and can recommend this little plugin for everyone running WordPress 1.5!
BotCheck for WordPress 1.5