You say this problem has occured suddenly and on three different servers in three different geograohical locations? I’d be hard pressed to say this was coincidence.
Start your trouble shooting by finding a common factor between all of the affected servers. New software, applied patches or hotfixes or even an updated AV deffinition file. Once you have determined a common factor, try rolling back or removing that object from your system and test. For multiple updates, follow this course of action one item at a time to isoloate the offending program.