Let me recommend you to use Configurable USB Loader. You may don't like the interface that well, but it's worth it.
USB Loader GX always has been kind of buggy from my experience.
After installing and using USB Loader Gx for months, one day it suddenly stopped detecting my external hard drive. I had not changed anything on the wii or the hard drive so i was puzzled at why this was happening. After trying to reinstall the wads and ios necessary for it to work and other usb loaders, i decided to follow the guide on this forum and re-soft mod my wii to make sure everything was up to date and i wasn't missing anything. It still wouldn't read my usb on usb loader gx or other loaders which were installed.
I have tried using various hard drives and none are detected on USB loader gx and i now get an error coming up when i boot the app. (problem with slow device...)
I have tried using my hard drive on others wiis and it works with no problems.
The hard drive is recognized by the wii on the homebrew, i can launch apps from it and installs wads from it and all other usbs.
After testing hard drive and usb ports on the wii there appears to be no hardware problems.
I have been searching for the answer to my problem for a while now with no luck and am getting really desperate because my wii is having problems reading some original games, which i had passed onto my external usb. I would really appreciate any help or suggestions as i really don't know what else to try and am not an expert on these things
You may also want to look at using WiiFlow for your USB loading needs. WiiFlow has much the same interface as GX and easier to use. A quick search can find all the information you need for Wiiflow.
Just downloaded it and tested it. Seems to have the same problem.. can't detect the usb storage device error (ret= -1)
I tried wiiflow before and had no success...
Tried this and still nothing Get Please wait.. then Please plug a usb hdd on port 0. Tried this on both my HDD and the 249 version too.