If try to enter a value using the summation+ key (don't know how to
get an epsilon here :-( ) or I try to clear the summation data (using
Clear -> CLEpsilon) I get a "Size Error" message.

Can someone tell me what to do to use these functions?

Thanks!

You probably already fixed this but...

The stats functions require a 25x1 sized matrix to be assigned to the
variable REGS to function.  Normally this is defined by default, but you
might have deleted it or modified it in some way.

I really don't like this about the 42S, I would like to create a better
solution.