I too have been configuring this.
In the dell bios, Intel Virtualization Technology... which I assume includes VT-d (direct IO); was enabled
reboot
Now in vCenter I selected all the USB related devices (exactly the same as your screen shot)... the icon went to "Reboot host required"
reboot ESX (vSphere4) server
Upon connection, the passthrough devices no longer appear. (was hoping for the green circle)
This link was the only other help on the issue I could find:
http://vm-help.com/esx40i/VMDirectPath/USB_Setup.php
One difference, the dell USB devices are off the root whilst in the article they are nested heirarchally.
Off to browse the vSphere logs.
I found no entries in Adminstration / System Logs / <vCenter node> mentioning either "adding" the above devices for passthru or removing them upon system start.
http://www.dell.com/downloads/global/products/pedge/en/server-poweredge-t610-tech-guidebook.pdf
http://en.wikipedia.org/wiki/Host_controller_interface
lead me to believe that we are NOT dealing with PCI usb. And could be the root cause...
If so, next step is to purchase PCI USB card and install on machine and see if passthru works then... notice in the ...USB_Setup.php link he uses a PCI device rather than the orphaned USB Controller device