Quick post before bed...
This happens with my Firepod, too. (Win7 x64 here)
Windows Task Manager shows Firepod.exe running in 32-bit mode. My guess is that even though the driver is 64-bit, the control panel itself is a 32-bit program and windows is using it's own bridge to open it. Maybe that's blocking REAPER from accessing it somehow? I'm not sure, I'm not really into programming..
You should still be able to access the control panel for your ASIO device from the system tray.