So far myself and two friends, both of whom are professional computer technicians, have been caught by the same thing in Network Manager. When adding a new WEP network the default code-type is "passphrase", as opposed to most network programmes, which ask you to key in the 128-bit key in Hex. I was lucky enough to notice and have used it happily since. Both of them, however, retried a few times, kept getting the (unhelpful) error message and gave up until I told them what would be wrong.
While I appreciate that it is a case of users not reading things properly, it is a mistake I can see a lot of people making and also something that I think we can prevent happening.
If we added a check along the following lines:
IF (AP uses WEP) AND (The passphrase entered fails) THEN
IF (Passphrase entered is 24 characters) AND (is only Hex characters) THEN
Try the passphrase as a 128-bit ASCII/Hex key
ENDIF
ENDIF
Then it would prevent this happening to others. I can't see that this would cause many other issues as such a small number of people would have a passphrase that was 24 characters and only hex. If they did then the worst that would happen is that it would try and fail to connect.
Linux developers are always talking about smart defaults. I think that if you gave a 24 character string, with only 0-9 and A-F in it, to a network-guru they would assume that it was a 128-bit WEP key; I see no reason why the computer couldn't make that same assumption.
I perfeclty agree with this suggestion. (Yes, I also entered my 128-bit key as a passphrase today ;-) )