The "Standard Solar Model" and the nebular model of forming the solar system are continually being changed to try to accomodate new experimantal findings.

It was changed to try to explain short-lived elements at the birth of the solar system.

It was changed to try to explain un-mixed products of nucleosynthesis in meteorites and planets.

Neutrino oscillations were proposed to try to fix one major problem.

The low O/C ratio in the photosphere is another unexplained observation.

Currently the SSM is being changed again to try to fit a 40% decline in the Sun's metalicity.

The SSM has been revised so many times that only the name remains.

Here are some of the observations unexplained by the SSM

http://web.umr.edu/~om/aasaapt.prn.pdf

With kind regards,

Oliver
http://www.umr.edu/~om