Okay, I found the sign error. We were looking at #8.59. I noted that there is a change in the mechanical energy of the system, due to energy being lost to friction. The mechanical energy is initially all kinetic (K1) and at the end state is all spring potential (U2).
So we know that
And the problem asks for the initial velocity of the mass, which I can figure out given the Initial kinetic energy:
We determined Wf to be -0.46J (friction does negative work). Where I got flummoxed was that I had dropped in -0.9J for the spring potential energy, whereas that is actually the work done by the spring- the spring potential HAS to be positive: +0.9J. Drat.
Anyway, the initial KE then is
K1=U2-Wf=(+0.9J) - (-0.46J) = 1.35J
From which I can calculate the initial velocity: 1.0m/s.