Oh, sorry, didn't see your posting before I replied. Well, I did try converting all vectors via the convert command but still couldn't get it to work. I might have made a minor mistake though. Not sure. So, altogether, might that suggest that vector components are referenced by vec[k] and matrix components by mat(k)? Why did I get it to work by the previously mentioned fix?

Thanks for you reply though!

Ok, I kind of figured this out...

The different subvectors seem to come out in different formats, because I can get this to work if I concatenate the vectors like this:

ConcVec:=[subv1(1),subv1(2),...,subv2[1],subv2[2]...]

I.e. components from some vectors called through brackets and some through parantheses.

Why does this happen? What determines this?