NotReadableException in Decoder.php line 20: Unable to read image from file ().

I've been getting this error for a while now on my IIS webserver and Intervention. Developing locally there is no issue and images upload nicely - all the files are identical and folder permissions are as I would expect them to be on both environments.

Bearing in mind this only happens on my IIS server and not my local Apache environment is it safe to assume the code is fine and it's a configuration issue? If so what should I be looking for?

Cheers!