Any idea what causes this message?

["Knute Johnson" <knute frazmtn com>]

Jan  5 03:19:30 www kernel: audit(1199531970.371:42): avc:  denied  {
append } for  pid=29639 comm="sshd" name="btmp" dev=dm-0 ino=2130022
scontext=system_u:system_r:sshd_t:s0-s0:c0.c1023
tcontext=unconfined_u:object_r:var_log_t:s0 tclass=file

I get these once in a while.  Can anybody tell what causes them from 
this?  F8 i386.

Thanks,

-- 
Knute Johnson
Molon Labe...