http://www.wiki-errors.com/err.php?wiki=503this maybe could be the answer, but not so sure. because everyone os configured differently. and another problem have you lately add some firewall or you have install some software.
This error often happen after user installing some software or firewall and misconfigured. roll back to the time you working fine that's maybe will help you.
My reccomendation. Dont ever use your server other than recharge purpose. you don't know when you will get virus. if you want play some porn movies, download mp3 use other computer don't mix with otomax pc. Otomax pc should be use only for transaction.
If you feel bored buy another pc put beside otomax for fun purpose this would save you alot of problem, even windows update won't mess your pc configuration.