[squid-users] sarg is printing nonsense

I have managed to get sarg working for a while. Recently however it has
started putting nonsense in the USERID column. Previously it used to put
the ip address of each computer that accessed the www in the USERID column
but now it prints a lot of nonsensical numbers - example below.

Any idea whats happening?

NUM USERID CONNECT BYTES
1 date/time 000000000000006 2.928 432 7.81%
677.78% 88.89% 00:00:00 0 0.00%
2 date/time 000000000000008 6.902 414 7.49%
1667.15% 92.75% 00:00:00 0 0.00%
3 date/time 000000000000002 4.301 347 6.28%
1239.48% 110.66% 00:00:00 0 0.00%
Received on Sat May 24 2003 - 07:19:12 MDT