I had the same problems with my Clippard solenoid. Mine is a little over a year old though (got it online), but I've only had it a month.
I was told to open it all up with the powercord unplugged. Then turn the psi up to 30 and plug the solenoid in with the needle valve all the way open. This should push out all sorts of debris. While the co2 is flowing out plug and unplug the solenoid several times. This helps push more debris out. After about 30seconds of this turn the solenoid off and spray EVERYTHING with compressed air. THen put it all back together and cross your fingers.
This didn't work the first time for me but the second time I tried it has seemed to hold up (like 3 weeks ago). Hopefully you can get yours working. Please post your findings in this thread as I am not sure how long my fix is going to last.