"signature collision error" Yikes!  I remembered this after talking with my boss.  I could not see the error as you have to click the little information icon on the left of the panel of the row where your "offline" drive is listed in diskmgmt.msc Then to fix, you right click the "red down arrow" in that same panel and select "online". Painful but easy to fix.
PowerEdge R210 II Windows 2008 R2: If more than 3 external USB drives are connected, they stay offline.  I am pretty frustrated with some odd setting (or I don't know what) that is stopping me from have more than 3 external USB drives connected to my server. The server pushes content to storage drives, currently network based SNAP servers, but I am migrating to External USB drives. I have a PCIe USB board with 6 ports and I am using the two rear ports for the KVM and the other for one more drive (and once this issue is solved I may use the two front ports for two more drives...) I have not posted here before, so I am not sure what I can provide (safely) in the way of system information.  Any help appreciated.  
PowerEdge R210 II Windows 2008 R2: If more than 3 external USB drives are 
connected, they stay offline.