I accidentally pressed the disable button on the stock gallery instead of the
Force stop button. In
Settings > Apps, the aplication moved to the end of the list of apps and says it's
Disabled. The only non-greyed out button is
Uninstall Updates. I have tried this several times, but it does not rectify the issue.
I believe the phone was autoupgraded from Gingerbread to ICS a long time ago if that is relevant. I have Quickpic installed, but there are no defaults selected.