I've thought about something that might be part of my problem.
I set a fix IP for the dongle, it gave me a submask automatically, but no gateway.
So I changed that and put for the dongle's gateway the same address as its IP.
Now I've got one/two silly questions and one problem.
The problem first : when I type "ipconfig/all" I get a different IP for the wireless connection (dongle) than yesterday. Is it normal ?
The questions :
Do I have to set some DNS too in the parameters of the wifimax ?
On the Wii, which IP, gateway, DNS do I have to input ? Those of the wireless or those of my computer Ethernet card ?