Aquarium Systems protein skimmer 100

[doxboi]

I have a Aquarium Systems protein skimmer 100. It has been up for about 8 to 9 months now and the thing is always releasing bubbles. I have a sponge on the return to try and help, but it is not.
It just started this. In the past it has worked fine until now. The cyclone looks good, but it just won;t work right. I changed the air hose and cleaned the sponge on the intake. What could it be? :help:

 

[jja]

Isn't that the same as a seaclone? If so I am having the same problem all of a sudden.