In re the post at http://www.fivedoves.com/letters/july2013/bruceb71.htm , the word translated "strength" in Ps 90 is "gibor", and it means strength, not pride.  God is described by this word in Isa 9:6 when it calls Him "El Gibor", which is translated "Mighty God".  My guess is that there was some confusion with the word "strength" (GiBoR) here and the word 3 words down, which is pride or "RaHaB."

Another thing to note is that Moses was complaining that people were dieing THAT YOUNG!  He was expecting people to live much longer than just 80 years.

Shalom,

Joe