Is this the same problem as your post at 1/x^2 (convex using DCP) ? if so, pick one, and show the full problem details. if not, show the full problem details here.
If you don’t see it listed in the CVX User’s Guide, it is not allowed. Multiplication of two CVX variables or expressions, as you have apparently done, is not allowed in CVX, except in Geometric Programming mode, which has its own set of rules.