android - Which Context to use? -

i'm writing android app, , have little problem regarding context.

i've read avoiding memory leaks article on android developers. suggest using application context instead of activity context avoid memory leaks.

the problem when that, app crashes on several places(using nexus s, although heard issue occurs other phones well).

so have 2 questions-

is familiar issue?

in general, context should use? if app written using activity context, , works fine, should try rewrite use application context?

don't use application because want avoid memory leaks. don't use unless know why using it. use it, article says, if creating objects live separately activity. these things definition should not doing things rely on kinds of things associated activity -- showing dialogs, etc.