I am not sure why they are crashing the computer, but you definiately want to be careful with an external RAID 1. Here is what I would try first in your scenerio:
1. Reset the drives somehow. Obviously you can't do this on the iMac, maybe by formating them one at a time on a PC.
2. Plug these drives in through a USB hub (possibily even a powered hub) since you can't connect the drives through each other. Then before you connect the hub to the mac, you should have the drives fully spun up (in manual power mode, switch on the back) and the hub and on before connecting it to the Mac. This way, both drives have a higher chance of appearing simulteanously to the Mac reducing any need for rebuilding because of out-of-sync issues.
3. I'd then follow the steps in this article to reformat the drives for your iMac again:
I've never attemepted a RAID 1 on external drives so you'd have to let me know how this goes.
If all else fails, you could jump in on an order the school makes with the following company and get an enclosure to tranfer your drives into. We have at least three of these enclosures at school, we are running one in RAID 1 and the other two in a RAID 0 configuration.
I finally found the time to do a zero wipe on both drives.
I'd actually used the exact same guide on my frist attempt, but had skipped the initial zero wipe part.
Unfortunately, I ended up with the same results... during the RAID 1 configuration, the OS crashed, and the drives would crash the OS whenever they were plugged in after that. I had to format them with a PC to fix them so that they wouldn't crash the iMac again. Who knew.
So I guess the iMac IS NOT able to handle a 2TB RAID1 configuration, even though it seems to think it can.
I guess we'll have to give up and either buy an enclosure or just use one of them as a Time Machine backup drive
Let me preface saying that I know nothing about a RAID setup; however....
there is one thing that caught my attention - may just be a typo (and have nothing to do with your problem), but I thought I'd ask:
Your original post says that you are running 15 GB RAM? That is an odd number, as the modules are supposed to match horizontally. Did you mean 16 GB?