After clicking the 'post' button for an AR cash batch, I received an error message that said
'Error adding record to G/L Transaction Details, record already'
and then the OK button.

The latest service pack was successfully done, and I have done used the AR for another set of accounts successfully since then.

What do you recommend I do from here :)) and have you run into this before

Kind thanks,

Whenever you see an unexpected message of this type, the first step is to make a backup of the data and run a DIC (File | Data Integrity Check).