NM quits WLAN connection if internetconnection is reset

If I drop my internetconnection on my router, network-manager-gnome shortly after disconnects from my local WLAN without any reason to. My router does not disable WLAN while internet is disconnectet, so it can be just by something on the ubuntu system, that disconnects from WLAN after loosing connection to the internet. Didn't happen in 12.10 before.

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: network-manager-gnome 0.9.8.0-1ubuntu2
ProcVersionSignature: Ubuntu 3.8.0-19.30-generic 3.8.8
Uname: Linux 3.8.0-19-generic x86_64
ApportVersion: 2.9.2-0ubuntu8
Architecture: amd64
Date: Sun May 5 19:33:55 2013
EcryptfsInUse: Yes
IfupdownConfig:
 # interfaces(5) file used by ifup(8) and ifdown(8)
 auto lo
 iface lo inet loopback
InstallationDate: Installed on 2013-04-28 (7 days ago)
InstallationMedia: Ubuntu-GNOME 13.04 "Raring Ringtail" - Release amd64 (20130424)
IpRoute:
 default via 192.168.81.254 dev wlan0 proto static
 169.254.0.0/16 dev wlan0 scope link metric 1000
 192.168.81.0/24 dev wlan0 proto kernel scope link src 192.168.81.136 metric 9
 192.168.122.0/24 dev virbr0 proto kernel scope link src 192.168.122.1
MarkForUpload: True
NetworkManager.state:
 [main]
 NetworkingEnabled=true
 WirelessEnabled=true
 WWANEnabled=true
 WimaxEnabled=true
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: network-manager-applet
UpgradeStatus: No upgrade log present (probably fresh install)
nmcli-con:
 NAME UUID TYPE TIMESTAMP TIMESTAMP-REAL AUTOCONNECT READONLY DBUS-PATH
 Kabelnetzwerkverbindung 1 f1c57fc5-77c3-422b-8393-f78bd98eb9ff 802-3-ethernet 1367649504 Sa 04 Mai 2013 08:38:24 CEST yes no /org/freedesktop/NetworkManager/Settings/2
 Auto wolfswald 64eecc48-37dc-41f1-aebb-513aa76df202 802-11-wireless 1367775204 So 05 Mai 2013 19:33:24 CEST yes no /org/freedesktop/NetworkManager/Settings/1
 E-PLUS VPN Connect 502c74d6-e12d-4b9a-bfa7-d01b273242c1 vpn 1367509770 Do 02 Mai 2013 17:49:30 CEST yes no /org/freedesktop/NetworkManager/Settings/0
nmcli-dev:
 DEVICE TYPE STATE DBUS-PATH
 wwan0 gsm disconnected /org/freedesktop/NetworkManager/Devices/2
 wlan0 802-11-wireless connected /org/freedesktop/NetworkManager/Devices/1
 eth0 802-3-ethernet unavailable /org/freedesktop/NetworkManager/Devices/0
nmcli-nm:
 RUNNING VERSION STATE NET-ENABLED WIFI-HARDWARE WIFI WWAN-HARDWARE WWAN
 running 0.9.8.0 connected enabled enabled enabled enabled disabled