Hello Ted,
sorry for the inconvenience you have, because of a silly bug of mine.
Your initial problem should now work with Maxima 5.19post:
(%i3) limit ((sin(n*x) - n*x*cos(n*x))/n^2, x, %pi);
(%o3) -%pi*(-1)^n/n
Furthermore, the following sign can be determined again:
(%i4) sign(-(1/n)*(-1)^n);
(%o4) pn
The reason for this bug has been, that (-1)*(-1)^n has simplified to
-(-1)^n, but not (-1)^n*(-1). We have got (-1)^(n+1). This causes an
endless loop in the function sign.
Dieter Kaiser