Gonna have to plug Robert McKee's book Story here, because he explains what prevents readers from getting bored when there isn't action happening REALLY well.
Basically, what McKee says is that in any given scene, there must be a change of state for the character involved from positive to negative or negative to positive. So, if something was going well at the beginning of the scene, by the end of the scene there must be a reversal (a complication arises, something falls through, etc.). Likewise, if the character starts a scene in a negative state (something has just fallen through, their love interest has just left them, etc.), then there must be a reversal of some sort into a positive state (a new solution arises, a new love interest appears, etc.).
(Or, put another way, if the scene starts with the character in a good state, something bad has to happen, and vice versa - doesn't matter what it is, so long as there is a change of some sort.)
So long as there is a change in state, something is happening and the reader will stay with you. If there isn't a change in state, then nothing has happened, and the reader will start getting bored. Likewise, this helps a lot in figuring out if a scene can be cut - if nothing in the plot has developed and nothing has changed for the characters, the scene is just wasted space.
Obligatory link to Story follows:
