B737-700
Flight Crew Air Transport Pilot (ATP)
Human-Machine Interface; Situational Awareness
Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Undershoot; Deviation / Discrepancy - Procedural Clearance
Aircraft; Human Factors
We were level at about FL330. ATC instructed us to cross NEWES at FL240. The crossing restriction was properly entered into the FMS and the jet started it's descent on time and on path.  Everything appeared normal. A couple minutes later; received a CDU message 'unable next altitude.'  I looked at the VNAV display and we were 1;100 feet above the path. I used the speed brakes but we crossed NEWES about 700-1;000 feet high. Cause for path deviation unknown: Winds were not a factor. More diligent monitoring by both pilots. Better FMS software.
Although they had programmed the the FMS to meet their ATC directed crossing restriction at NEWES; the Flight Crew of a B737-700 failed to note they were more than a thousand feet above the required descent gradient until the the CDU advised them they were not going to make the restriction.  Herculean flight crew efforts failed to overcome the deficit.