I have the same problem but my Drobo is connected via Firewire already, The disk pack vanishes from Finder, Disk Utility etc and after a couple of minutes suddenly reappears. Strangely enough a second Drobo (connected via Firewire to the first one) stays visible on the Mac. Both Drobos run the latest firmware version.
This just happened to me on Mac OS X 10.6.5, I had previously had issues with my TomTom deciding to disconnect itself half way through a sync since updating to 10.6.5, although TomTom has just released an updated client that fixes this issue.
I have a support ticket open regarding this very issue, I only see if on one machine. On other machines I haven’t been able to reproduce the problem but Apple have checked out my machine and can’t find anything wrong with it, also it’s only the Drobo I see this problem with - other firewire drives work without issue.
Maybe opening another ticket will help in tracking this issue down.
I am having the same issue. It’s making be totally buggy. I already lost my itunes library, when the drobo freaked out and disconnected it apparently corrupted it.
It’s impossible to get even stupid things (like clearing out my phone to my iphoto library) without freaking out and dropping. It’s comforting to know that I’m not alone, but really annoying that it’s not being addressed.
Now to figure out how to fill out a support ticket.