Unable to trim - change trim data/type

Hello,

I'm trying to model an impeller but it's giving me an error which I can't seem to solve on my own. I've created a curve that represents the centre line of the impeller vane. The curve gets extruded untill extended (impeller hub / impeller cover plate) but I can't change the offset (thickness) of the vane. It'll give me an error that the trim data or type is not good.

I've tried all the different options but I'm stuck at this point. Any help or thoughts as to what might cause the error?