networking - Ubuntu 12.04, sony vaio T11, no hardware wifi button, networkmanager "enable wireless" unavailable

My Sony Vaio T11 does not have a hardware button to enable/disable wifi. When I disable wifi in NetworkManager and reboot "enable wireless" is not available (grayed out) in Networkmanager.

$>rfkill list wifi
0: phy0: Wireless LAN
    Soft blocked: yes
    Hard blocked: yes
1: sony-wifi: Wireless LAN
    Soft blocked: yes
    Hard blocked: yes

Different to similar problems of this kind "rfkill unblock all" does not help.
However I can boot into windows, start the wifi there and when I reboot to linux wifi is working again.