The sheer number of posts for this error (8504,104 versions 4 to 6) & the repetition of steps to resolve the issue suggests that Symantec/Norton do not have a clue and that the product is, in fact, 'not fit for purpose'.
Personally, I have encountered this error too many times to keep count & have uninstalled/reinstalled N360 an equally high number of times, to no avail.
The most recent occurrence led me to what seemed like a new set of steps to 'fix' the issue - but sadly this also failed, pretty much at the first hurdle - having followed the steps to use the Norton Power Eraser, this tool failed to start after the reboot, leaving me no option but to 'disable' the rootkit scan & run the tool manually.
On completion, a list of 'possible' causes was presented, but the 'Fix' button was not available (faded out), again leaving me no alternative but to perform a 'cloud scan' on each item, one at a time, none of which turned out to be a real threat/issue.
