  One interpretation of proton stability is the existence of extra-flat
directions of the MSSM, in particular $u^{c}u^{c}d^{c}e^{c}$ and $QQQL$, where
the operators lifting the potential are suppressed by a mass scale $\Lambda$
which is much larger than the Planck mass, $ \Lambda \gae 10^{26} \GeV$. Using
D-term hybrid inflation as an example, we show that such flat directions can
serve as the inflaton in SUSY inflation models. The resulting model is a
minimal version of D-term inflation which requires the smallest number of
additional fields. In the case where $Q$-balls form from the extra-flat
direction condensate after inflation, successful Affleck-Dine baryogenesis is
possible if the suppression mass scale is $\gae 10^{31}-10^{35} \GeV$. In this
case the reheating temperature from $Q$-ball decay is in the range $3-100
\GeV$, while observable baryon isocurvature perturbations and non-thermal dark
matter are possible. In the case of extra-flat directions with a large $t$
squark component, there no $Q$-ball formation and reheating is via conventional
condensate decay. In this case the reheating temperature is in the range $1-100
\TeV$, naturally evading thermal gravitino overproduction while allowing
sphaleron erasure of any large B-L asymmetry.
