Windows 2003 R2 and TCP Offloading Troubles

I'm running an MPI application which broadcasts extremely large
packets (150MiB-3GiB) over the network at regular intervals during
execution. With TCP Offloading enabled through Windows 2003 R2's SNP
(Chimney I believe) I run into an issue where the application hangs
sending the data. On Windows 2000 Server or with TCP Offloading
disabled on Win2k3, this does not happen.

Moreover, this happens on multiple MPI implementations (MPICH.NT and
MPICH2) and on multiple types of network cards (NC373i and NC380T and
NC7782). The only common point left in this problem is Windows 2003 R2
and TCP Offloading.

Has anybody seen this issue before?