The problem has been solved.
Evidently, the byte array that I was sending in to the Integration Server from the Enterprise Server was automatically being converted to a string.
However in my IS Service, I was trying to convert the input byte array (which was actually already a string) to a string using the byteToString built in service. It was this service that was throwing the exception. Thus removing this service rectified my problem.
Thanks for responding,
Mark
#Integration-Server-and-ESB#webMethods