I've since discovered several other websites have the same problem.
When I double-click on the status bar at the bottom of my IE window, I see the following errors have occurred:
Webpage error details
User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)
Timestamp: Mon, 13 Dec 2010 21:39:55 UTC
Message: 'Bootloader' is undefined
Line: 32
Char: 1
Code: 0
URI:
http://www.facebook.com/
Message: 'Bootloader' is undefined
Line: 34
Char: 1
Code: 0
URI:
http://www.facebook.com/
Message: 'BigPipe' is undefined
Line: 62
Char: 1
Code: 0
URI:
http://www.facebook.com/
Message: 'big_pipe' is null or not an object
Line: 63
Char: 1
Code: 0
URI:
http://www.facebook.com/
Message: 'big_pipe' is null or not an object
Line: 64
Char: 1
Code: 0
URI:
http://www.facebook.com/
Message: 'big_pipe' is null or not an object
Line: 65
Char: 1
Code: 0
URI:
http://www.facebook.com/
Message: 'big_pipe' is null or not an object
Line: 66
Char: 1
Code: 0
URI:
http://www.facebook.com/
Message: 'big_pipe' is null or not an object
Line: 67
Char: 1
Code: 0
URI:
http://www.facebook.com/
Message: 'big_pipe' is null or not an object
Line: 68
Char: 1
Code: 0
URI:
http://www.facebook.com/
Message: 'big_pipe' is null or not an object
Line: 69
Char: 1
Code: 0
URI:
http://www.facebook.com/
Message: 'big_pipe' is null or not an object
Line: 70
Char: 1
Code: 0
URI:
http://www.facebook.com/
Message: 'big_pipe' is null or not an object
Line: 71
Char: 1
Code: 0
URI:
http://www.facebook.com/
Message: 'big_pipe' is null or not an object
Line: 72
Char: 1
Code: 0
URI:
http://www.facebook.com/
Message: 'big_pipe' is null or not an object
Line: 73
Char: 1
Code: 0
URI:
http://www.facebook.com/
Message: 'big_pipe' is null or not an object
Line: 74
Char: 1
Code: 0
URI:
http://www.facebook.com/
Message: 'big_pipe' is null or not an object
Line: 75
Char: 1
Code: 0
URI:
http://www.facebook.com/
Message: 'big_pipe' is null or not an object
Line: 76
Char: 1
Code: 0
URI:
http://www.facebook.com/
Message: 'big_pipe' is null or not an object
Line: 77
Char: 1
Code: 0
URI:
http://www.facebook.com/
Message: 'big_pipe' is null or not an object
Line: 78
Char: 1
Code: 0
URI:
http://www.facebook.com/
Message: 'big_pipe' is null or not an object
Line: 79
Char: 1
Code: 0
URI:
http://www.facebook.com/
Message: 'big_pipe' is null or not an object
Line: 80
Char: 1
Code: 0
URI:
http://www.facebook.com/
Message: 'big_pipe' is null or not an object
Line: 81
Char: 1
Code: 0
URI:
http://www.facebook.com/
Message: 'big_pipe' is null or not an object
Line: 82
Char: 1
Code: 0
URI:
http://www.facebook.com/
Message: 'big_pipe' is null or not an object
Line: 83
Char: 1
Code: 0
URI:
http://www.facebook.com/
Message: 'big_pipe' is null or not an object
Line: 84
Char: 1
Code: 0
URI:
http://www.facebook.com/
Message: 'big_pipe' is null or not an object
Line: 85
Char: 1
Code: 0
URI:
http://www.facebook.com/
I don't imagine this is a browser problem. Why would both browsers suddenly produce the same error?
It's probably not a website problem, either. Seems to point to Windows. But I didn't purposely or knowingly change anything, and a system restore to the day before I first saw the problem didn't resolve the issue.