Pleask+IIS Creating Mess In Server!

[hackedia]

Hi I' Using Plesk 12.5 With Windows 2012 Datacenter And I Have A Website I'm Hosting My Site From A Dedicated Server With Main Domain eg www.mydomain.com and i'm using my vps server for hosting files with sub domain eg : dl.mydomain.com but the problem is IIS or Pleask Is Making My VPS Server Down Don't Know From Where Everytime Needed to Restart The Server I Think Problem Is Accuring In IIS not sure!
So Any Idea How To Fix This Problem? and yes 1-2 days ago http 503 error also happened on my subdomain ... site!