i'm having trouble installing games from disc with ANY of my usb loaders - USB Loader GX, wiiflow, and CFG Loader all have this problem. basically it'll just get stuck around the 1% mark (seems to vary depending on game size - the smaller the game is, the more progress it'll make before getting stuck. 1% is with Mario Galaxy 1, a smaller game like Wii Music made it to around 24% before getting stuck). I've tried tons of different flash drives, all either 13GB or 32GB (all of them SanDisk except for one, which is a Verbatim one.)
Don't use a flash drive, they have too many issues, use a HDD instead.