CANNOT ACCESS WEB PAGE FROM INTERNET

I WORK AT A BUS COMPANY AND WE HAVE A VERY BASIC WEB SIGHT WITH JUST HTTP, TODAY USERS COULD NOT GET TO OUR SIGHT. THE ERROR WE ARE GETTING SAYS HTTP: 1.0500 SERVER ERROR LOGON FAILURE THE USER HAS NOT BEEN GRANTED THE REQUESTED LOGON TYPE AT THIS COMPUTER.WE CHECKED OUR PERMISSIONS AND THEY WERE O.K. WE ALSO CHECKED THE LICENCE MANAGER AND CLEANED THAT UP, WE FREED UP SPACE ON THE SERVER WHICH IS RUNNING NT3.5 AND WE STILL HAVE THE SAME PROBLEM, I WOULD APPREACIATE ANY SUGGESTIONS. THANKS IN ADVANCE TGEREMIA@CENTRO.ORG