Hi Ronny,
Im guessing that youre using the original hot end? If you are it might be clogged and since its a pain in the a** to clean.
I will suggest that you get either a J-head or even better an E3D Head with the 0.4 nozzle, you can get it at http://e3d-online.com/
After i switched i have only had a single clog after about 3 months of usage. You will ofcourse need another extruder construction like the one i've got (check my Solidoodle upgrade thread)
And if you cant print it yourself i'd be more than happy to print you one