Zanussi DE6544 flashing lights?

Grateful if someone could help me with this.
When I try to start the wash cycle the SID & Normal lights flash but there are no other signs of activity from pumps etc..
This happened a couple of days ago and I removed the bowl filter, took off the pump impellor cover and cleaned out the green filter thats inside the bowl. Did'nt fix it immediately, but after pulling on the drain pipe it burst into life. Worked OK for a while but its failed again with the same symptoms.
I reckon its a blockage somewhere, but not sure where.
Are there other filters I've missed?

Many thanks for the help.

Martin A
November 2005