I was in the workshop yesterday and there was a Porsche 996 in to have the air-conditioning condensers replaced because they were corroded. This is a very common problem with Porsche 996s and Boxsters. The condensers (and the engine coolant radiator) are mounted inside the front bumper and dead leaves and other rubbish get caught up around them. This then attracts and holds moisture which, in turn, leads to the mild-steel radiators corroding and, in time, the air-con gas or coolant will leak out.
So, the moral is to ensure that you regularly clean out these areas or, even better, invest in some mesh grilles to stop leaves entering through the front intakes.