It isn't called Edge III because of the springs.
Ibanez originally had the Edge, then the Lo-Pro Edge, then various Edge II and Edge III and now the top-o-line Edge-Pro.
Edge III is a great trem... I'm almost positive you are over tuning, or don't have enough springs.
You can get springs from my friend over at
"IBANEZ RULES!!" - Ibanez Guitars - New and Used, his name is Rich, from New Jersey (USA) and he'll fix you up. ALSO his website has the BEST info for setting up Ibanez guitars with this sort of trem.
Don't forget I'm very experienced with the Lo-Pro Edge, so ask any questions you need to.