Is anyone using H.323 gateways, and do those gateways have the 'Media Termination Point Required' checkbox checked in the CallManager Gateway configuration page? There is a bug CSCdy87397 which might come into play, but I'm not sure it's present in 3.3(3)sr3.
If you don't absolutely need an MTP in the middle of your conversation (and most deployments don't), it is safe and desirable to leave that checkbox off. However, if it's already off, it might be worth a try to turn it on, or turn it off if it's on. When an MTP is in the middle of an H.323 call, the way supplemental services such as hold, resume and transfer work are much different. Changing the setting could produce a change in the problem for better or worse, or no change at all, but the outcome would be of diagnostic interest in any case.
I have worked with Mr. Aronhalt in person on some other issues, so I have some knowledge of his AVVID topology. I note with interest that he and the original poster are running the exact same version and service release of CallManager, with similar if not identical phone loads. I reviewed the release notes for the newest 3.3(3) service release, which is 3.3(3)sr4a. I can't see any bugs fixed between there and 3.3(3)sr3 that apply here, so I don't know if it would help to apply it.
