@ Theo Cooke
I do have a couple reported cases where Connections has trouble on MAMP, but I do not have a Mac so I can really debug why it doesn’t work. This is odd because on production servers it runs fine. So that tells me it is definitely a server config issue, but I could not tell you where to look or what to change, sorry!
Maybe you could try this this version [pre-lease to an update comeing this weekend]:
It has an updated script library for image processing and removes a couple deprecated PHP functions among many other changes.