swraid problem

Hi list,

Server TSL2.2 is set up with 3 scsi disks.
/ is raid1 (mirror) of 3 partitions
/home is raid5 of 3 partitions

This is all set up during install, like I've done many times before,  
but mdstat looks bit odd:
root@server ~# cat /proc/mdstat
Personalities : [raid1] [raid5]
read_ahead 1024 sectors
md0 : active raid1 sdb3[1] sda3[0]
       2939776 blocks [3/2] [UU_]

md1 : active raid5 sdc4[2] sdb4[1] sda4[0]
       577922176 blocks level 5, 64k chunk, algorithm 2 [3/3] [UUU]

unused devices: <none>

Looks like sdc3 is not used by md0, so I add it like:
root@server ~# mdadm --add /dev/md0 /dev/sdc3
Segmentation fault

Now mdstat shows:
root@server ~# cat /proc/mdstat
Personalities : [raid1] [raid5]
read_ahead 1024 sectors
md0 : active raid1 sdc3[-1] sdb3[1] sda3[0]
       2939776 blocks [3/2] [UU_]

md1 : active raid5 sdc4[2] sdb4[1] sda4[0]
       577922176 blocks level 5, 64k chunk, algorithm 2 [3/3] [UUU]

unused devices: <none>

Anyone has a clue what is going wrong here?

Thanks,

Ariën