Sitemeter is back in business. Apparently, they updated the script but did not take into account some bugs in Internet Explorer, thus the error messages users experienced the other day. If you want to read the technical details, you can find it in the Microsoft user support pages.
I re-installed the Sitemeter script but this time, I did not use Blogger's Add Page Element feature. Instead, I added the script before the /body tag. (You can find my Sitemeter at the bottom of the page.) This would prevent the same problem from happening again in the future. (I hope!)