A_ride_4_ever -- did you ever get resolution on this? I've got the same configuration you have, and have the SAME problem. MSL 4048, at least on of the drives go off line after a small period of usage. I've been working with HP on this for almost three months. At least I've gotten it down to a process --- library goes offline, stop BE services, power off library, power on library, wait 10 minutes, start BE services. For a while, we couldn't figure out which combination would get things to work again, but this seems to make it go. Once the library is offline and I've stop BE services, I run LT&T and it comes back with errors communicating with the library. After power cycling the library, it sees it just fine. From that point, I would think it has to be a communication problem, and not a BE problem, but HP is not coming up with anything.
Just looking to see how you made out on this.
Thanks!