vowels typed on a mac are all preceded by 'e'

[jason shaw 0]

Using latest versions of Synergy (downloaded and installed today - 29/12/15) on a Windows 10 64 bit PC (the server) and iMac El Capitan 10.11.2 (the client). Works great but whenever I type a vowel (in web browser search window, MS Word etc ) the vowel is always preceded by an 'e' e.g. if I try to type aeiou I get eaeeeieoeu I saw a similar post recently but in that case vowels were being duplicated rather than preceded by an e. I am using a standard wired PC keyboard on the PC, and a standard wired mouse. Any ideas? many thanks