RHEL5: TCP connection to a specific TCP port fails - Red Hat Customer Portal

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Issue

This RHEL5 client fails to generate a SYN packet only when it tries to connect to any remote IP at one specific TCP port number, 9xxx.
Connections to 127.0.0.1 or the local client IP address at port 9xxx work fine.
netstat/ss show the socket in SYN_SENT state, but no SYN packet is ever seen on a tcpdump taken locally with -i any.
Connections to any other port number work perfectly fine!
No iptables rules. We unloaded all their netfilter modules and it did not resolve the issue.
SELinux is disabled
No obvious error seen in netstat -s

Environment

Red Hat Enterprise Linux 5.11
- kernel-2.6.18.398.el5
Java
Vmware
- e1000 NIC driver

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