I'm starting to become more functional in Mathcad, so I wanted to take the opportunity to look into known drawbacks, mathematically speaking, of CAS/computer math systems. For instance, one of the exercises we did in school involved "breaking" TI Derive by asking for the limit of a discontinuous function (at the point of discontinuity, of course). Another example would be p. 13 of this;
So basically, I'm hoping folks will contribute known problems with these kinds of apps, whether from their experience with a particular package or generalized problems inherent in computer algebra.
I myself am most concerned with Mathcad and Mathematica, but it would be awesome for people to talk about CAS/computer math in general and drawbacks of various systems (matlab et al) in particular.