My mistake: that version of the Trend Micro software that I mentioned in my previous post didn’t fix the problem after all. Thanks to this comment in response to my first posting on this subject I learned that the specific component of the TM software package that’s causing the problem is the spam toolbar that is optionally installed in Outlook. When I tried using the debugger immediately after installing the new version the problem was not present, but that was because I hadn’t yet turned on the toolbar. I tried it again after turning the toolbar on and the same problem with the debugger log returned.
At least I can use the rest of the package now. Sadly the spam filtering is one of the most useful parts of the package.