What Have I done AGAIN?!

Sigh.. Think I've somehow, unknowingly, or I should say innocently upset/ made my friend angry. Really, not my fault what! I've told a couple of friends, guys & gals, they gave me the same answer," No worries, you not at fault!" Yeah, I felt truely relieved and glad that third-parties think I'm at no fault. But clear enough, her MSN nick has indicated that she's disappointed and upset coz I so-called "fly her aeroplane" by not joining her for an activity. In the 1st place, I DID NOT promise her anything. Really...How?? Sigh...this is not the 1st time that we have misunderstanding. But, it always turn out that it seems like my fault which I choose to differ(from her view only, coz no other people think I'm wrong leh). To salvage the friendship, I'm always the 1 who apologises. Thou i didn't feel it's my fault, especially this time round. I'm getting sick & tired of it. ARGHHHHHHHH