Is it possible to set XDCAM 330, or 350 to "pause record"? For example, I would like to stop in the middle of a recording without creating a new clip.

Nope, i don't think that's possible. You can effectively recreate the effect in camera though by creating a clip list and surgically removing portions of clips to playback as a cliplist file.

-gb-

and, it's not a bug, it's a feature! ;-)