I made it to Petalburg City where I took a break off the game. When I came back every time I try and load the game a box appears instead telling me:
Script 'SaveData' Line28: TypeError occured.
incompatible marshal file format (can't be read) format version 4.8 required; 0.0 given
Followed by the OK button which closes the box when I click it.
If anyone knows what I need to do then please tell me I'm very confused!