I just tried avast 4.1.304 with Word 97 on Windows ME, and I don't see anything wrong.
So, a few more questions:
1. You are using the latest build of avast! (b. 304), right?
2. Did you change some other settings of the Standard Shield (such as turning on the "Display of detailed info on performed action"?
3. If you run a scan on your hard drives (or in particular, the drive with your system and office installation, macros, documents, etc.), no viruses are found, right?
4. How do you disable avast so that the problem disappear? You remove ashServ.exe from the auto-start registry key?
5. Does the "freeze" occur every time you try, or just sometimes?
6. What other programs are running at the time you try (i.e. what programs/tools are automatically started when your Windows start)?
7. If you start Windows, select "Stop on-access protection and exit" from the system tray avast icon, and then start Word, does it help?