A user doesn't show up with a name in your setiqueue before he has uploaded a result successfully, or asked for wu and gotten from Berkeley. Since these 3 users has never done anything of the sort, they're showing up as blank in SetiQueue.
Oh, and the e-mail-address was removed from user_info.sah in 2001 or something... At the same time some other info like country was also removed from user_info.sah
Anyway, a little poking around shows:
4796509 is Lynxx
registered 27.11.2003 at 02:15:14
28277 results; 305480697.190847 seconds cpu-time
4683123 is LynxxKlamm
registered 06.09.2003 at 03:16:50
2895 results; 24925546.041504 seconds cpu-time
4674522 is esilent
registered 30.08.2003 at 01:15:38
2826 results; 22925860.987133 seconds cpu-time
Of course, both results & cpu-time will increase next time a result is successfully returned.

The easiest to find should be the 1st, since this has largest production...
edit -- on the class-pages, all 3 shows up with names & Germany.