#3. "RE: 3200 ASA setting when using AUTO mode" In response to In response to 2 Thu 14-Jun-12 03:23 PM by elec164
As JP suggests, using the Green-AUTO (or any of the scene modes) will by default place you into certain settings. Some of those settings can be over-ridden while some cannot.
Looking at the D5100 Reference Manual it appears that the Green-AUTO mode puts you into Auto-ISO with no ability to change it. So as JP suggest you may need to lower the maximum ISO setting for Auto-ISO to possibly prevent that from happening; or don’t use Green-AUTO mode when faced with such situations.