Not impossible to believe. Mathcad 14 and 15 use a different symbolic engine than Mathcad 11. At least two of the places where the sheet hangs are rather trivial to solve by hand.
However, since the sheet already has the solutions for the places where the sheet hangs, you can simply disable everything in the top portion of the sheet without any detriment to the end result of the sheet.
TTFN
