I have had the same issue on several occassions. It is my believe it is more of a hardware issue as the USB port seems to be initiated on different moments with different hardware.
So, to test if this is the issue for you to, start SRD (from BESR8?) without USB connected and test the following scenarios:
- When the "Press F6 key ..." appears, plug your usb disk
- As soon as the Windows colour screen appears, plug your USB disk
- When you get the EULA, plug your usb disk
For every scenario, let SRD start and check if you can see your disk
For my environment I needed to wait until 40-60% ot the "F6" msg befor I can plug my usb disk and have it recognized...
Regards