QNX 4 with TCP/IP

I encountered the following when trying to interface a PC with a server
via TCP/IP.

Could not ping server from a PC with Net.rtl (RealTek) and QNX 4.
Could ping itself and the localhost

Could not ping server from a PC with Netether1000 and QNX 4.
Could ping itself and the localhost

Could ping server from a PC with 3Com driver and QNX 4.

The hub hardware that allows us to connect to the server is made by ODS
and the part # is 294-TFR.

As a test, we brought a spare Netgear 4-port hub and connected
it in series between the existing network outlet jack and the PC.

When we did this, we were then able to ping the server with the PC’s
that could not ping above (using the Netether1000 and the Net.rtl
drivers).

Any ideas as to why this might be so?

Thank You.

Dan Szymanski