Believe it or not, all you have to do is look on the back of the unit and it should say what version it is, right after the serial number. Depending on the version you have, it might be incorporated right into the UPC sticker, or it might be an add-on sticker right next to it.
Are you using the default OS (msn companion) or win98? If you ARE using msn companion, and have NOT yet updated to version 2.0, then that is why it will not work. You MUST have 2.0 to use a USB adapter. I have verified this myself with a version 3.0 adapter - it did not work with msn v1.0, but did with v2.0.
Also, my version 2.1 adapter did not work with the IA-1 with either version of the OS.
After updating the OS to v2.0, the indicator light on my v3.0s (note - not just one but all of them) did NOT work when connected even though it was working perfectly.