Hey,
Just to let anyone else know, I flashed back to the original bios and now my machine boots great with perfect graphics and no strange USB thing in the top bar. This was F20e, I'm back on the F2 bios and it's great. Apart from the extra clover entries. So be warned if you're on a GTX 750ti, you might not be happy. I'm also on iMac 17,1 with the graphics patch to fix the 5k retina thing.
I'm going to try F5d bios next and see what happens re: clover entries and graphics.
Yep F5d is the sweet spot for me. No more multiple entries, graphics all working as they should. No USB icon in the top right tray. YMMV but for me, it's spot on now.