My USB is flakey, too. I upgraded to WinME and it seemed to help, but my USB network adapter still causes blue screens on occassion. It's weird... it either works flawlessly, or it craps out on me quickly.
I got the "Registry Error" when I tried to install the 4-in-1 drivers, too. I think it's because your HD controller device in the Device Manager shows a yellow exclamation mark. Try manually installing the 4-in-1 drivers (there are two INF files in there... right-click on both and choose the Install option). Then install them again normally... the registry error should go away.
Also, see if your USB filter drivers were installed correctly. Even though the install program says it installed properly, there's a file that comes with the drivers called VIAUSB.SYS that doesn't get copied into my \WINDOWS directory or in any of its subdirectories, which makes me think that either A) the install program is screwed, or B) the I-Opener doesn't need the USB filter driver. Actually, when I try to install an older version of the filter driver (1.06), it tells me that my system doesn't need it.