Server :: No Input On Serial Console?

I've got a home server running ubuntu 10.0.4. It have no monitor or keyboard. So I want to access it from a serial console. (I use SSH currently but if something goes wrong, I need to be able to do something... so serial console seems a fine thing). OK, so on the server, I tell grub to output everything on ttyS0 and opened a getty on ttyS0. On the client side (Laptop running Ubuntu 10.0.4 with pl2303 USB to Serial adapter) I use Minicom.

Home server restart:I see grub menu, linux kernel messages, login prompt. But, I can't do anything:In grub or at the login prompt, no key press is recognized by the server.I've got write permission to /dev/ttyUSB0. I tried a different getty (mgetty)with no success.I stopped the getty on ttyS0 on the server. And run minicom.

From the server's minicom, if I type something, it appear on the client screen. From the client's minicom, if I type something, some garbage appear on the server screen :(One of this things for each char typed). If I short-circuit pin 2 and 3 of the client serial port, it echoed what I type. The two serial ports are connected with a nullmodem cable. (seems to be a full handshaking cable). Of course, same serial port config for both minicom, grub and getty. Hope I'm understandable enough. (English not my primary language). Can somebody help me make this *$*#! serial console working right ? I'm on it for 10 hours now with no success...

Edit : I nearly forgot to tell you I had to update the standard ubuntu kernel to 2.6.34-020634rc1-generic because there was a bug in the pl2303 driver in the stock kernel (2.6.32-25-generic) which prevented me from doing anything (even receiving).