'99 ES300, had the car for almost 3 months.
A little while ago I was investigating the cause of the power mirrors (replaced "CIG" fuse) and AC not working (yet to solve) and when I wrapped that up, suddenly the front windows won't go down.
No noise or anything. The rest of the master switch works. Just neither front switch on driver or passenger side switch works. I couldn't find any fuse that could be a culprit, at least not listed in the manual; not sure about relays. I'm assuming it's a greater electrical issue than the motors or regulators since it's both at once.

 

Welcome to my world.I have a 9 ES 300 BUT i HAVE HEARD MANY OF THESE MODELS THE MOTORS AND REGULATORS GO BAD IM REPLACING MY DRIVERS FRONT TODAY DID THE PASSENGER FRONT YESTERDAY NEVER DONE IT AND IT WASN'T EASY TOOK ME 4 HOURS.YOU CAN TEST THE MOTOR BY UNCLIPPING IT AND RUNNING A WIRE FROM THE MOTOR TO THE BATTERY AND TO REVERSE IT JUST REVERSE THE WIRES YOU ARE RUNNING TO THE MOTOR I CHECK MY SWITCHES FIRST ALSO -14 DOWN +14 UP ANYWAYS IT SEEMED EASIER FOR ME TO JUST BUY THE WHOLE ASSEMBLY AT THE JUNKYARD BY ME YOU TAKE YOUR OWN PARTS OFF I GOT BOTH FRONT FOR 50 MY YEAR 96 THE ARE EXPENSIVE NEW I SAW ALMOST 300 ON A FEW AND SAID NO WAY I GOT MINE USED WORKING FINE WELL ONE IS.MY PROBLEM WAS PASSENGER MOTOR DIED AND THE DRIVERS SIDE THE CABLE SNAPPED ON THE REGULATOR.YOU CAN EASILY CHECK YOUR MOTOR IF YOU KNOW HOW TO TAKE IT OFF I DIDNT KNOW HOW SO I GOT THE WHOLE THING.ANYWAYS LEXUS I HAVE SEEN MANY MANY PEOPLE SAYING THE SAME THING THE JUST WEAR OUT OVER TIME IN MANY OTHER CARS ALSO.