Lars, my Epson Stylus C82 has a similar affliction; when not used for a while the ink clots up and doesn't print very well.

On the front there's a button with an ink drop above it, normally used for telling the printer you want to change the ink cartridges. If you hold this down for three or four seconds, the printer will clean the head instead and let you print again.

I use my printer so rarely that I have to do this nearly every time.