[blue68f100]

Have you tried a different cable or port?
Did you install Reg EEC memory?

I had problems with my 4500 when I installed 4 400gig Seagate HD. I pulled the HD's and ran SpinRite on them. I had 1 HD that had terrible seek errors. It also had quite a few bad sectors. Seek errors will cause major problems on RAID's arrays. SpinRite built the bad sector table so the SMART Tech did not have to do this on the fly, causing timming errors. After running SpinRite a couple of times on the bad drive with seek errors, they seamed to settle down. I think spinrite may have tunned the HD.

btw, I run SpinRite on all of my HD's, new and once a year. This builds the bad sector table so helps with timing. This tells me if I'm going to have problem with the drive.

Raid Arrays require a lot of cpu power.