Unity 5.3 - Vuforia issue for iOS

Hi,

I've just upgraded to Unity 5.3 - it appears to have broken one of my projects which is an iOS project using the Vuforia SDK.

This is the error I get.

Error building Player: BadImageFormatException: Format of the executable (.exe) or library (.dll) is invalid.

I haven't come across it before, does anyone have any suggestions please?

P.