Interesting bandwidth limitation on w2k server

[NDGeist]

I've got a customer using a Marathon Array for their PDC/fileserver.
They are seeing a really odd bandwidth limitation when uploading from the PDC:

From a BDC(not a marathon array, just standalone server) they can upload at ~100Mbps (to PDC)
From a BDC they can download from PDC @ 100Mbps
From the PDC, they can upload @ ~100Mbps (to another machine on lan)
From the PDC, they can download (from BDC) @ only ~30Mbps...

the hardware all appears to be working, but why can information be downloaded from the machine fast, but not uploaded from the PDC's console?

Thanks in advance
CT