Reserve Maneuver (PHB2, p191):
Benefit: Choose an encounter attack power from your class. The power must be your level or lower and one that you don’t already have. When you regain the use of your powers at the end of any rest, you can gain the use of the chosen power instead of regaining the use of an encounter attack power of the same level or higher.
Does the highlighted "from your class" include the class I multiclassed into?