I’ve been getting this a lot too. I have a Drobo with four 2TB drives at about 75% full (3.7TB used). I had this configuration working flawlessly for almost a year formatted NTFS and running on Windows, then I bought a MacMini and it all went downhill (I love Apple stuff and am writing on a Macbook right now, but the MacMini was definitely not for me). So… I bought a DroboShare because it was too painful to even think of reformatting as HFS+, but I found the DroboShare was too slow, so I laboriously moved all my data onto about 7 other hard drives (most borrowed) and reformatted as HFS+. I got all my data back onto it without incident, but soon after I started experiencing the problem you are experiencing - random disconnects.
The problem for me is I’ve now returned the MacMini (partially because I blamed it for my Drobo problems, wrongly it seems), so I’m now copying all my data back onto some new hard drives I bought on a new PC so that I can reformat the Drobo as NTFS, but its still doing the same thing to me even when connected by the DroboShare. It’s as though the Drobo is dropping it’s USB connection to the DroboShare just as the directly attached Drobo did to me on the Mac.
My gut feeling is that this has to do with it being formatted HFS+ for Apple devices, since it was when I did that that all my problems started, and yours is presumably the same formatting. Rather than guessing what the problem might be though, I’ve just logged a support call and sent them my diagnostic log file. I’m at the point where I can’t trust the device with my data now, rendering it useless, because once I lose connection on the DroboShare I end up in an ugly reboot cycle where all the lights go red and my heart stops as I fear the worst even as it happens for the 6th time.
I so want to love my Drobo, but it’s not easy at the moment.