I'm gonna bump this, since I have a similar problem.
I previously installed cIOS 36 rev 10 and wanted to try using USB loader 1.5 and/or usb loader GX.
HDD gets detected, no problems there, I can format it, I tried backing up one DVD (which froze and gave me some code dump, but I suppose it's because it's a bad DVD which caused problems when playing from it, too).
Anyway, I still have a few unburned isos on my computer and ofc wanted to back them up to the usb drive. Formatting works, drive gets detected in the two wbfs managers I tried afterwards (tried WBFS tool and WBFS_Gui). I then backed up one of the isos to my HDD via those tools, takes a few minutes and everything seems to work flawlessly. When done I unplug the USB drive, plug it into the wii and in both, USB Loader 1.5 and USB Loader GX the games don't show. Both of them actually show several totally blank lines which I can scroll up/down through, but when I press "start" the program freezes. USB Loader GX also shows "Number of games 14" and "Disk Space available 298 of 298 MB"
Anyone got a clue what's wrong there?
Also after unplugging the USB drive from my PC once, it won't show up when I plug it again (makes the USB connection sound but does not show up as a drive). So I have to go through the PC-management and have to start it as a "new logical drive" which of course automatically deletes the wbfs format and I have to start over again.
Specs:
Wii 3.2E
cIOS 36 rev10
no other IOSes installed whatsoever (could that be an issue?)
USB Loader 1.5 and/or USB Loader GX
Wiikey 1.9g