I can't speak for Neutrino, having never used TFTP there, but under QNX 4 tftp can only handle up to 32 megabytes, due 
to a packet counter overflow feature/problem. Furthermore, while dealing with that issue, I ran across another version 
of tftp, quite a bit older, that could only handle up to 16 megabytes; this was due to a bug in the implementation. The 
latter was an old "official" Berkeley distribution, dated 1993, that was still being used on the project. I believe that
, if you are having either of these problems, you will get the "retry count exceeded" error.

It is possible for tftp to handle files of infinite size, but both the server and the client have to agree on the packet
 counter format to do so. I personally have not encountered that situation.