Internet Explorer script error: Line 53, Character 3

Anybody know what the heck this is? I've been seeing it over and over again on websites of all sorts. It appears whenever I try to close the page I'm on. The above example is from Gort's Gort42, which is a Blogspot blog. I'm also seeing it on Gareth's Another Chance to See, which is also a Blogspot blog, as well as Isis the Scientist's On Becoming a Domestic and Laboratory Goddess (NEW ScienceBlogs version) - which is not a Blogspot blog. On many other sites I'm not seeing the problem at all.

The remedy that I have found is to click the "Yes" button, or sometimes the "No" button, or sometimes both, about a gazillion times. The fun part comes on the gazillion-and-first click, after the message has closed and you've just randomly clicked on whatever happened to be under it.

I know, I know: Who uses Internet Explorer anymore? Use a real browser, like Firefox! Well, I use Internet Explorer, and so do a heck of a lot of other people. And as far as I know, Firefox hasn't resolved this problem, though their open-source philosophy suggests that I should say that Firefox users haven't resolved that problem.

I tried looking information up on this problem the other day but could only find scattered bits and pieces. I'm guessing that this is another one of those little bugs inadvertently written into Internet Explorer that requires an elaborate and precise workaround and creates an incompatibility with stuff that works perfectly well in other browsers that hasn't had the workaround applied. But that's just a guess. Maybe on my days off I'll look into this more closely.