I usually start multistart puzzles by resetting the puzzle the number of times to cycle through all the possible starts, and moving them around as I load each one to examine them.

In both puzzles 516 & 517, every time I tried to click on the white space to move the puzzle around, it drew a band from the protein into the point where I had clicked on the white space (with an arrow) - as if I had clicked on a segment and pulled the protein. But the band did not appear until I had moved the mouse.

I found that clicking once on the white space, then clicking again to turn the puzzle around did work. Mac OS 10.6.8