Help with my sky plus box no satalite signal recieved?

I have a thomson sky plus box nearly 3 years old. We have recently exteded the cable so we can move it to the other end of the room. We were getting signal fine until today when the error messageis displayed on the screen. We have checked the cables and they *seem* to be ok, what else could cause this problem.

Signal strength and quality are both at about 75 %
inout 1 lock inicator - not locked network id - 0000 transport stream - 0000

Many thanks

Jemima Holding
April 2009