A (probably) dumb protein skimmer question

[SmallFry]

I've had my Euro Reef RS100 running for a while and I'm having issues with the fact that the foam isn't breaking down in the collection cup and overflowing. It's not just going crazy and frothing with clean foam it's pulling dirty skimmate which is really nasty when it does break down in the cup. It just seems to be pulling too much. I haven't been adding anything to the tank to cause it to go nuts either...

I'm wondering if I'm skimming too dry and the foam is too loaded with organics for the bubbles to burst? Would raising the water level in the skimmer make it skim wetter so the foam breaks down?

I'm a bit lost because this is the first skimmer I've had that will actually pull anything out.

All suggestions welcome..

Rob