[Exim] Mail not deleivered

I have notice that email is not being delivered on a server, the log says

2004-05-07 20:41:25 1BMBDo-0001tm-Ia unable to set gid=101 or uid=100
(euid=102): local delivery to <SNIP> transport=local_delivery
2004-05-07 20:41:25 1BMBDo-0001tm-Ia failed to read delivery status for
ron@??? from delivery subprocess
2004-05-07 20:41:25 1BMBDo-0001tm-Ia appendfile transport process returned
non-zero status 0x0100: exit code 1

Any thoughts ?