Problems with USB Loader GX with my Wii?

I have USB Loader GX on my Homebrew Channel and it plays downloaded games fine. But if I copy a game to my USB hard drive using USB Loader GX and try to play it (The newly games appear in the play menu) from the Wii It goes to black and the goes back to the Homebrew Channel without playing the game. What am I doing wrong? Is my USB Hard Drive compatible? I tried WiiFlow but it would not read my USB Hard Drive. Any help would be appreciated! Thanks..........