Raid 5 steup problems w Ubuntu Server 8.10

I am experiencing great problems setting up a Liunx Software Raid 5 system.

My motherboard is a ASRock K10N78-1394 which has 6 SATA connectors. I have set them to work in AHCI mode.
My disks are Seagate's 1.5 TB. I want them to be used as five active and one spare.
My boot medium is a 4 GB USB memory...
The installation CD/DVD drive is also connected via USB, if that's relevant.

First of all, I have read the post on Tom's that issues a warning about my disks: http://www.tomshardware.com/news/seagate-barracuda-1-5TB-freezing,6558.html and I haven't seen any kernel error like that one yet.

Now, the only time I can access the disks without any comments about "device busy" or "missing super block" or similar, is from the rescue mode shell prompt from the installation CD. Here I have built the entire array three times (each time for about 10 hours). Even if I boot up in single user mode, the drives are "busy".

I use mdadm 2.6.7, and I have zero'd the super blocks before creating the array. Last time, I installed ReiserFS, and one of the disks failed (might have been a freeze, acually) which caused a rebuild. Afterwards, I could mount the array but only in this rescue mode.

Now, as other people are waiting for this server to be up and running, I really need help with this one fast. If you know what's wrong, or what components must be replaced, please tell me. Would it help to get a new SATAII controller?

The disks each have one single (huge) partition. Is there an upper limit for what these tools can handle? Anyway, next time I try (if there will be one) I will shrink these partitions. Their type is set to FD.

Any mdadm command I have tried from the regular prompt has resulted in an error - most often "Device or resource busy", but also "invalid super block" and "Input/output error".

Commands issued:

fdisk - basic stuff
Disk /dev/sdb: 1500.3 GB, 1500301910016 bytes
255 heads, 63 sectors/track, 182401 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x9146d6b7

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1      182401  1465136001   fd  Linux raid autodetect

mdadm --zero-superblock /dev/sd{a,b,c,d,e,f}1
mdadm -Cv /dev/md0 -l5 -n5 -x1 -c128 /dev/sd{a,b,c,d,e,f}1
mkreiserfs /dev/md0
- These last ones work fine in rescue mode and I can follow the process in /proc/mdstat.

After reboot:

$ sudo mount -t reiserfs /dev/md0 /mnt
mount: wrong fs type, bad option, bad superblock on /dev/md0,
       missing codepage or helper program, or other error
       (could this be the IDE device where you in fact use
       ide-scsi so that sr0 or sda or so is needed?)
       In some cases useful info is found in syslog - try
       dmesg | tail  or so

/proc/mdstat reports my failed disk (sda) as spare (S).

$ sudo fsck.reiserfs /dev/md0 --rebuild-sb
reiserfsck 3.6.19 (2003 www.namesys.com)

Will check superblock and rebuild it if needed
Will put log info to 'stdout'

Do you want to run this program?[N/Yes] (note need to type Yes if you do):Yes
bread: Cannot read the block (2): (Invalid argument).
reiserfs_open: bread failed reading block 2
bread: Cannot read the block (16): (Invalid argument).
reiserfs_open: bread failed reading block 16

reiserfs_open: the reiserfs superblock cannot be found on /dev/md0.

I am attaching /var/log/messages and dmesg output. Anything else needed?