Hi, Steve:
It could be a number of things. The first thing that comes to mind is that interrupts may have been disabled prior to the "wait" instruction. Besides waiting, the "wait" instruction also enables interrupts. Try replacing it with a "cli" instruction.
Also keep in mind that the "wait" only waits until an interrupt occurs, and will continue with your code after any ISR completes. So it may not be necessary to remove it.
