In the period 1947-1970 where wages were increasing, I don't know. Perhaps it had to do with legislation like the G.I. Bill, which increased human capital during that period and could have helped trend wages upward:

http://en.wikipedia.org/wiki/Gi_bill

America is not a pure capitalist society. We have free public education, for instance. Capitalism also has obviously good effects, such as increased productivity and relatively efficient distribution of goods and services without central control. Profits from these effects can be distributed in the form of wages, if that's what employers choose to do.

In terms of the crisis, again I'm not sure. You'd have to consider not only the losses of the crisis, but the gains of the boom. Who benefited from the boom, and did those gains survive the bust?

19th century Marxist theory doesn't have the answer, but it frames these issues in an important way. Rather than crises and falling wages as abberations from normal steady growth, they are considered part of the capitalist system.

For a more modern perspective in the Marxist tradition, check out Max Weber or Georg Simmel. There are even radical, almost psychadelic strains of Marxism like Foucault, Deleuze and Guattari.