yeah I have the same WD 2.5 S-ata drive, get the odd KP, restart and open up Console and noticed the same (same-ish) line, de bug called for during Windows resize, that's probably why it seems to KP when surfing (regardless of browser) but any kind of resize operation seems to trip a KP, using Cover-flow etc.
I agree with you it seems to be a drive issue, some WD (none Mac Branded) drives don't index properly in Mac, well know bugbear.may be even the paging memory who knows
swap it out, what I'm going to do, easy fix, with a fresh instal would be wise. Like the look of the seagate drives, pretty cheap these days, keep to the same spindle speed. 5400