Comment 4 for bug 138917

Reading the patches that went into 0.6.5-0ubuntu11, its probably 41t_nm_device_wireless_index_ctrl_sockets_by_run_count.patch thats causing the problems, more specifically the hunk:
@@ -2808,27 +2822,30 @@
                wpa_driver = "madwifi";
         else if (!strcmp (kernel_driver, "hostap_pci") || !strcmp (kernel_driver, "hostap_cs") || !strcmp (kernel_driver, "hostap_plx"))
                wpa_driver = "hostap";
        else
                wpa_driver = "wext";

        /* wpa_cli -g/var/run/wpa_supplicant-global interface_add eth1 "" wext /var/run/wpa_supplicant */
        if (!nm_utils_supplicant_request_with_check (ctrl, "OK", __func__, NULL,
- "INTERFACE_ADD %s\t\t%s\t" WPA_SUPPLICANT_CONTROL_SOCKET "\t", iface, wpa_driver))
+ "INTERFACE_ADD %s\t\t%s\t" WPA_SUPPLICANT_CONTROL_SOCKET "%d\t", iface, wpa_driver, self->priv->run_count))

Which seems to add an integer to the end of the command, making the path invalid (/var/run/wpa_supplicant exists on my system, /var/run/wpa_supplicant2 does not...)