Can't seem to run a USB Loader GX restored ISO game from my USB drive.

This is what i've tried..Anyone had similar or see what I'm doing wrong.

Successfully managed to dump my 4 games to USB disk using USB Loader GX.
I can launch them and they run fine.
I then used the PC utility to read the WBFS partition and choose to convert the wii sports to an iso file. This comleted and i deleted the original from the USB drive, then as a test I restored from the ISO file on the PC. The restored game would not load on the Wii, just a blank screen. The other games which had been originally dumped direct to the drive from the Wii still worked fine.

Cheers
Nick