Spacebar not working (Ubuntu server / MAC client)

I am having the following problem. When I press spacebar on the server, the client receives this sequence META+SHIFT+Z. Thus, I can't input any space in the client.

Server is an Ubuntu 11.10, client is a MACBOOK pro with Lion.

I have the same problem both with latest 1.4.x and with latest 1.3.x.

Here is the log of client when I press space:

recv key down id=0x00000020, mask=0x0000, button=0x0041
mapKey 0020 (32) with mask 0000, start state: 0000
find best: 0000 0000
best key index 0 of 4 (exact)
found key in group 0
state: 0000,0011,0011
flip: 0011 (0000 vs 0011 in 0011 - 0000)
desired state: 0000 0011,0011,0011
flip: 0000 (0011 vs 0000 in ffee - 6020)
mapped to 007, new state 0000
keystrokes:
038 (00000000) down
039 (00000000) down
007 (00000000) down
039 (00000000) up
038 (00000000) up
recv key up id=0x00000020, mask=0x0000, button=0x0041
keystrokes:
007 (00000000) up