ct_connect() - Perl

Hello all,
I really need your help here.
So i have 3 servers:
Source A
Destination B
Destination C


On my Source A i'm running a perl script that uses ct_connect() function. I was working fine 2 weeks ago.
Now it works fine with Destination B, but if fails with Destination C gives me the error:

! Open Client Error: 4 (Layer 5, Origin 3, Severity 5)

ct_connect(): network packet layer: internal net library error: Net-Lib protocol driver call to connect two endpoints failed

! Operating System Error:

Failed to parse address info

This issue could be due to the interfaces file on Source A, however the interfaces file is OK and has not been changed since years... Also I can use ISQL to connect to Sybase server on Destination C, so again the interfaces file is ok.
I'm sure that the script is using the same interfaces file.

Any idea? Network issues, firewall?

Thanks a lot