[font=trebuchet ms]You can do some small tweaks (like slacking off the strings one-at-a-time and rubbing the tip of a sharp pencil in the nut slots - cheap graphite lube), but the tuning problem is an inescapable result of the design. Some very complicated attempts to address this issue (like the Floyd Rose trems) are better at holding tune, but [u]all[/u] trem designs are the net result of someone's choices and compromises.

You could have a tech do some work on it, like installing locking tuners and opening up the nut slots a bit. These things will help a bit, but there will always be some string slippage.[/font]