Ok, before I try to get deep into what might be the problem(s), lets start with the very basics ok?
Cool

When you create a particle object or an emitter emits a particle object, Start Frame is set to 1.0, by default. The value is the duration of a single frame in the current setting for time units.

Now this is the important part:
If you change the time units setting, you must set the Start Frame to the correct initial value so that Maya computes the start time again.
An emitted particle object accepts emitted particles only at frames greater than or equal to its Start Frame.

For example, to emit particles at frame number -5, set the Start Frame of the emitted particle object to -5 or less.


So, have you made sure that you setup your particle object/emitter like the above?

Double check and let us know, so we can proceed with other ideas