If there isn't a skin on top, I bet its just that the yeast aren't flocculating. Do you know much about your water? If you have low levels of calcium, for instance, or some calcium coarbonate or some such... some trace mineral anyway, that has something to do with calcium... calcium carbonate??... Sorry, can't remember. Point is this: if your low on some trace minerals it only adds to the flocculation problems. I bet cold-crashing will do a lot to clear it up, though, if thats the case.