If it was PC, I'd ask you what those plugins have for extensions. Anyway, it usually happens if you have an extension like ... pst, for instance, used by a program. If you install another program that uses the same extension for something else, you'll notice that all the files with that extension became associated with the program later installed. the problem is, I think that Mac doesn't uses the associations like Windows. Nevertheless, have you tried deinstalling everything and then installing Bryce first and those two afterwards? How can Bryce claim folders BTW?

-- erlik