First, make sure you got it in USB slot 0, looking at the back make SURE its on the right side, the side closest to the edge. Also try a newer version of your loader, and the last suggestion I have is to try a wii backup manager on the computer and tell it to go to wbfs, and if that does not work your flash drive will not work, and if it does you did not format it correctly to fat32. If you do format it to wbfs, make sure all of your content is backed up. (i had a flash drive that would not work as fat 32, but when i made it wbfs it would)
Also, if you have an ISO of a wiigame on your computer, you can try moving it over with the backup manager.
I didnt catch that you were using a flash drive. Regardless, what is the model # of the drive you are using? Is it on the compatibility list?
In all of my plug/un-plug iterations, at some point I switched ports and mistakenly began using Port #1. All is well now.