So it has the same problem. Somehow Gerrelt seems to be able to work around the problem with his manual set-up script.
It could be because I use -b with the udhcpc command instead of -n, which the wifi.tcz script uses.
From the udhcpc man page:
-n Exit with failure if lease is not immediately obtained
-b Background if lease is not immediately obtained
So, -n exits with a failure if, after certain time, the lease is not obtained.
With -b the process goes to the background and keeps waiting until a lease is obtained.
Our Raspberries aren't the fastest machines, so -b might be more suitable then -n.
Also if your network or router isn't very fast, -b might be more suitable too.
This is the result of using -n :
udhcpc (v1.21.1) started
Sending discover...
Sending discover...
Sending discover...
No lease, failing
Failed to connect.
Have you tried my wpa_supplicant.conf and wifi script?