remus is right, I was configuring a trivial SAMBA based sharing, and almost broke my head revising the SAMBA documentation for this constant halting with TC 4.2.1 and SAMBA 3.6.1. I even resorted to put a hole 1 GB of RAM to the server machine, but it still went unresponsive after a few seconds!
On the other hand, and even downgrading to just 128 MB of RAM, TC 3.8.4 + SAMBA 3.4.5 allowed me to transfer a 16 GB file from a Windows machine, without a hassle. Hope this gets a workaround for an upcoming 4.x release, either it's caused by SAMBA or the TC kernel. Anyways, thanks for the effort to everyone involved.