Fail to connect using serial console

[serial console]

Server: DL360G4P
OS: RHEL3 (Update 8)
Description:

We try to connect to Red Hat system, using null cable. We can connect it at a very beginning.

Then, we install lrzsz-0.12.20-10.i386 for file transfer.

The process of transferring files from Windows machine (HyperTerminal) to Red Hat server (HP DL360G4P) is smooth. BUT, the transferring procedure hangs up and cannot transfer files any more. I then force to break the transferring process and try to connect to the Red Hat system again. However, I fail to connect it becase there is no response shown on screen.

Do you know what the problem is and how to get it fixed ?

[Alexander Chuzhoy]

Try to reboot your machine.
It could be that the process didn't die correctly.