Hi Renee1964
Odd! What version of MYOB are you using - see Help About AccountRight. And are you accessing the online file from the desktop application or from the browser option?
With MYOB (AccountRight Desktop application at least) each employee 'card' has a consecutive RecordID (or Employee ID) allocated by the database. This is the only field that cannot be set by the user, and cannot be changed by the user. However what can happen is if a user opens a pay transaction for Mr X from say the transaction journal, clicks the arrow next to Mr X's name, this will open Mr X's card. If the user changes all the name and address details to Ms Y, then every transaction and entitlement balances etc will change to Ms Y.
Check you do not have 2 Cards for Ms Y. If you do, look at both Employee IDs. The earlier number will probably actually belong to Mr X.
Regards
Gavin