Well, too late as I just came here to say I have uninstalled Avast and reinstalled AVG. I did not have any AVG routines running in memory, and nothing that in startup was AVG, so as my problem was Avast not starting every time I started win98se I cannot see how that is an AVG problem. For example, I booted win98se and no Avast, repaired and rebooted and Avast started no problem. Switch off PC to have a meal, booted win98se, and no Avast again. It's very annoying.
Also with regards you having Avast a long time ago and it worked, maybe as with all software, when win98se was still the top OS, companies spent more time on testing the win98se version. Now the feeling is everybody has XP (which is far from true), most of the testing is done in XP and not as much in win98se. So whereas your version, say 2.8, worked, maybe 4.6 does not.
Anyway, spent enough wasted time trying to get Avast working, gave it more time than most would have, so have just gone back to AVG, which as I say, is a resource hog, but it works.
Avast works without a problem in my XP, so I will keep it on there.
As regard dual booting, I have had this system for nearly 3 years and have no system problems. I would bet XP owners have more problems running DOS/win95/98 games then I do because I have kept my dos/win98. So overall, while I have the occasion problem with a game in 98 I know I would have many more if I only had XP to work with.