Baycom-modem not receiving?

[Rea]

Today I wanted to migrate my packet-stuff from a pentium-75 running Win95 to
a IBM PS/2 77 (486DX2) running Linux.
Setting it up was no problem, but now the IBM-machine isn't receiving any
frames... TX goed well, I think I configured the ports OK.
I tried under DOS and have the same problem. I think it's hardware
related... The baycom (TCM3105) is working fine on the Pentium.

Any Idea's ??? I'm sorry if this is off-topic, but I wouldn't know where to
go else...

Best Regards,

Remco