[dexen]

Perhaps the Funarg problem [1]:

>The difficulty only arises if the body of a nested function refers directly (i.e., not via argument passing) to identifiers defined in the environment in which the function is defined, but not in the environment of the function call.

Also, the version I know has much more bite:

>There is also a variation on this that says there are two hard things in computer science: cache invalidation, naming things, and off-by-one errors.

[1] http://en.wikipedia.org/wiki/Funarg_problem