Problem: "invalid argument" emitted by sendTo

[mgross@dorsai.org]

I am using SocketPrim to send a udp packet to each of 254 addresses on a
network. The message packets have been preconstructed and placed in a
list, whose content has already been checked for correctness and appear
to meet the specifications in the appropriate RFC. When I go
through the list (using mapM_), sending a packet to each address with
sendTo, I get a valid return code from sendTo (used trace to check that) 
for the addresses from 10.129.129.1 through 10.129.129.239. Address
10.129.129.240, however, fails with the messages

Fail: invalid argument
Action: sendTo
Reason: invalid argument


The message "invalid argument" does not appear within the source of
SocketPrim, but it does appear in several of the binary files in the
library. I've begun to dig around in the source code, but I've taken to
hoping that someone out there in Haskell land may be able to point me
directly to where (and for what) I should be looking to determine just
what triggered those messages. 

Oh, yes, verson info: ghc-5.00.2, linux (debian testing). 

Thanks in advance for attention. 

Murray Gross
mgross@dorsai.org