OK -- I reinstalled Opera, and it seems to be working. I saved the .adr file before uninstalling the previous program, and then just swapped it out for the new one. Joy!

I also downloaded URLBase (see Bill D's link above), and it seems to be just the ticket for importing my bookmarks into IE.

Thanks again to everyone who helped!

BTW, I recommend Opera ("the fastest browser on Earth"!)

Cheers,
Michael