The plastic Exustar cleats really do wear down quickly, Dave. It's normal to have to replace them. I go through 2-3 pairs a year, which is a pain, but you have to keep on top of it to keep yourself safe. No point saving a fiver then pulling your foot out at 30mph.
I'd start by replacing the worn cleats. (Any chance of a photo of them, just to see how much wear and tear there is?)