Logic Not Reading/Writing Midi Information Correctly

I am new to Logic and to the world of midi in general -- so please go easy on me. Here is the problem I am having:

I am using an M-Audio Keystation 88 Pro with a Roland EV-5 Expression pedal plugged into the volume control. When I play software based instruments with this set up (such as Garritan's Solo Cello) everything sounds fine. But, when I record the performance in Logic 8 and play it back, it appears that Logic 8 is playing back incorrect Midi info. For instance, if I do a crescendo from 0 to 127 using the expression pedal and record it, Logic plays it back in a way that sounds like it starts out at around 127 and then drops to a lower number and kind of "flutters" back up into the crescendo.

I am not sure what is causing this and any help would be appreciated.