Oh well, IE 8 Beta 2 is not compatible with McAfee AV
I updated IE to IE 8 Beta 2, but unfortunately it is not compatible with McAfee Anti-virus, so I had no choice but to revert to IE 7. Oh well.
The problem symptoms were that clicking on an email message subject line in Outlook Express took several seconds to repaint the OE window and left it blank for most of that time, plus the McAfee SecurityCenter window would always come up blank, so that you could not check status or change settings.
I found a message on a McAfee discussion forum which basically says that the problem is known but that no fix should be expected until IE 8 comes off of beta status.
So, I am back to using IE 7 as my system default browser, but I still use the new, non-beta version of Google Chrome for most of my browsing.
I will play with Chrome for another week or so and then decide whether to make it my system default browser.