L4 IPC doubt

[Tiago Jorge]

hello to you all.
Let me describe my cenario...
I have my L4 server that receives ipc calls. The code was generated from 
DICE. And i have a lib and i've implemented a client that uses that lib.
My L4 server also uses ipc to comunicate with other servers, mainly with 
flips that also uses IPC.
that problem is the following:
My client makes an IPC call and blocks waiting for the answer from my 
server... while processing that answer, my server has to comunicate with 
flips using IPC.
The problem is here... my server blocks in the ipc_send when calling 
flips, but when i remove the call from the client it works fine, meaning 
that the client is not blocked waiting for ipc to return. My questions 
are... why can't i do IPC while another one that has nothing to do with 
my server is blocked? there can be only one ipc call in the whole system 
at a time? they all must be sequential?

thanks in advance

Tiago