Istar connection problem

I hope someone can help me with my Unix to Unix connection problem using Istar. Here's the setup: Boxes A and B: IBM 720's running Solaris 2.4 with Informix 5.06.UC1 Box C: HP K410 running HP/UX 10.10 with Informix 7.12.UC1 Box D: NCR 3445 running AT&T SVR4 2.03 with Informix 5.02.UC7 I am testing connections between these boxes using dbaccess database@servername I can connect between boxes a and b. I can connect between boxes c and d. I can connect from box c to boxes a and b. I CANNOT connect from boxes a and b to box c. I always get the error message -408 ( invalid message type received from the sqlexec process ). Tech Support so far has been unable to help. I have the identical service configured in sqlhosts and /etc/services - hebstar1 using 1542/tcp. I have all my connection priveleges set. I have .rhosts configured to allow connections without passwords ( tested this using rlogin. ). I have tried using different protocols in the nettype field of sqlhosts - both olsoctcp and oltlitcp. It makes no difference. I reinstalled online and istar on boxes a and b - no difference. Any ideas? Thanks in advance. Mike Ballentine