  Recent progress in solar Hard X-ray (HXR) observations with RHESSI data and
methods for spectral inversion allow us to study model-independent mean
electron flux spectra in solar flares. We report several hard X-ray events
observed by RHESSI in which the photon spectra $I(\epsilon)$ are such that the
inferred source mean electron spectra are not consistent with the standard
model of collisional transport in solar flares. The observed photon spectra are
so flat locally that the recovered mean electron flux spectra show a dip around
17-31 keV. While we note that alternative explanations, unrelated to electron
transport, have not been ruled out, we focus on the physical implications of
this tentative result for the collisional thick-target model.
