Similar to "jerking your chain", this is phrase is used to say "just kidding". It is rooted in the common helpdesk response to "Check your spam (email box)" when an intended email did not reach it's destination. As if the recipient did not think of that...; Shortened version: jus' chanckin'
Maybe you should log off and reboot in safe mode....nah, just Chanckin' yer Spam. Your computer's fucked.