Firstly, the reason why your serial log is so jumbled is that Hyperterminal is crap. It is a terrible app and the only redeeming feature is that it is bundled with most versions of Windows.

"Error -4 occurred at disk p" isn't from the default empeg software. Have you been running smartctl? smartctl will print out errors along the lines of "Error <blah> occurred at disk power-on lifetime: "