4.3 to 4.2a backwards compatibility??

Hi, i'm just back from the Boston conference and had carried out a bit of work on a model in 4.3 at the demo stations. I'm using 4.2a on my machine and the model won't open, just getting the message;

'Model created with a later version of COMSOL'

Has anyone else had this issue and how can I resolve it?

Cheers in advance!