Ubuntu Servers :: High I/O Wait After Every Reboot?

The Machine

Core 2 Duo E4600
2GB DDR2 RAM (1 stick)
Intel ICH10R based motherboard (tried an ICH9R aswell)
4-port SATA controller (PCI Sil 3114)
O/S: Ubuntu Desktop x64 10.04 LTS (using 'desktop' because I like having a remote desktop)

The Storage Setup Disks: Assorted selection of 9 disk. 750GB, 1000GB and 1500GB Seagate and Western Digital disks. The disks are joined through a standard LVM2 configuration. I don't know the LVM term, but normally you'd call it a JBOD setup. On that LVM device, I've put a cryptsetup device, made with the LUKS tools (aes-xts-plain 256) On the cryptsetup device, I've created and mounted an EXT4 partition.

All in all, a completely standard LVM2 and LUKS setup, running EXT4. After a reboot, I proceed to unlock my cryptsetup encryption device, and then mount the EXT4 partition. All is well, the mount is accessible and everything looks fine. I then try to send a file to the mount, via Samba. After a few hundred MB written, the I/O wait goes berserk. It stays at 50% (dual core setup remember). The system becomes unresponsive to network commands (can't browse samba) for about 5-10 minutes. When it finally responds, the I/O wait is gone and everything is now fine. I can write and read hundreds of GB's of data without any issues at all. I can benchmark and stress all disks perfectly fine and no logs are showing disk errors.

I tried monitoring my disks with 'iostat -d 2' while the I/O wait was happening, and there is some slight Blk_read/s activity on 1 disk at a time. First for example /dev/sda is showing a little Blk_read/s acitivty, then it jumps to the next disk, and when every disk has show that slight Blk_read/s activity (500-800 or so) the problem is gone and the I/O wait is no more. I've tried changing motherboards, switching disks around on the controllers, checking individual disks, replacing disks and I've tried different versions of Ubuntu. The problem however persists. I could see it being a network issue, possibly a driver issue. But since the NIC is a standard RTL8111 on-board it seems unlike that the problem wouldn't be more widespread since this NIC is litterally being used everywhere. I did change my motherboard, so a faulty NIC seems unlikely twice in a row.