Does TFTP work through NAT on NW65 / BM3.8? (Both at SP2)

We've just setup Cisco 7940 VOIP phones and they can't receive TFTP config
files from a PBX outside BM. The phones work fine once the filter exceptions
to the PBX are configured, they just can't receive TFTP config file updates.

NAT is setup for static and dynamic.
BM works fine (GWIA, WebAccess and other Accelerations) and has no other
Workstations and VOIP phones are not using Proxy, just NAT.
BM has been optimized per Craig Johnson's recommendations.
Unloading filters has no effect.

If TFTP does not work through NAT, does anyone have a recommendation?