I have a Dell Latitude D820 laptop with both Ethernet and WiFi. Normally, both are on, though it doesn't seem to matter in this case. Both interfaces are configured to be managed by the NetworkManager.

[root@umka ~]# grep NM_CONTROLLED /etc/sysconfig/network-scripts/ifcfg*
/etc/sysconfig/network-scripts/ifcfg-eth0:NM_CONTROLLED=yes
/etc/sysconfig/network-scripts/ifcfg-eth1:NM_CONTROLLED=yes

The PowerDevil is configured such as that the system will be suspended upon laptop lid close:

[root@umka ~]# grep lidAction ~vag/.kde4/share/config/powermanagementprofilesrc
lidAction=1
lidAction=1
lidAction=1

Upon the cold boot, everything runs just fine, the interfaces are properly managed, etc.

[root@umka ~]# nmcli nm status
RUNNING         STATE           WIFI-HARDWARE   WIFI       WWAN-HARDWARE   WWAN      
running         connected       enabled         enabled    enabled         disabled  
[root@umka ~]# nmcli dev status
DEVICE     TYPE              STATE        
eth0       802-3-ethernet    connected    
eth1       802-11-wireless   disconnected 
[root@umka ~]# nmcli con status
NAME                      UUID                                   DEVICES    DEFAULT  VPN   MASTER-PATH                                 
System eth0               5fb06bd0-0bb0-7ffb-45f1-d6edd65f3e03   eth0       yes      no    --       

After I close the lid, the laptop goes into the standby (suspended, sleep) state just fine and when I open the lid later, it wakes up properly too.

However, after the wakeup, the network is down. The Network Manager Applet Icon that looked like plugged-in RJ-45 connector, now looks as a big white "X" on the red background. 

The new state looks as follows:
[root@umka ~]# nmcli con status
NAME                      UUID                                   DEVICES    DEFAULT  VPN   MASTER-PATH                                 
System eth0               5fb06bd0-0bb0-7ffb-45f1-d6edd65f3e03   eth0       yes      no    --                                          
[root@umka ~]# nmcli nm status
RUNNING         STATE           WIFI-HARDWARE   WIFI       WWAN-HARDWARE   WWAN      
running         asleep          enabled         enabled    enabled         disabled  
[root@umka ~]# nmcli dev status
DEVICE     TYPE              STATE        
eth0       802-3-ethernet    unmanaged    
eth1       802-11-wireless   unmanaged    
[root@umka ~]# nmcli con status
NAME                      UUID                                   DEVICES    DEFAULT  VPN   MASTER-PATH                                 

As you can see for whatever reason, NetworkManager fails to wake up (STATE="asleep")

Now, I can wake it up manually and bring the connections up:

[root@umka ~]# nmcli nm sleep false

All the connections come up as they were before the suspend.

[root@umka ~]# nmcli nm  status
RUNNING         STATE           WIFI-HARDWARE   WIFI       WWAN-HARDWARE   WWAN      
running         connected       enabled         enabled    enabled         enabled   
[root@umka ~]# nmcli dev  status
DEVICE     TYPE              STATE        
eth0       802-3-ethernet    connected    
eth1       802-11-wireless   disconnected 
[root@umka ~]# nmcli con status
NAME                      UUID                                   DEVICES    DEFAULT  VPN   MASTER-PATH                                 
System eth0               5fb06bd0-0bb0-7ffb-45f1-d6edd65f3e03   eth0       yes      no    --                                          

However, another problem comes up. After that, the laptop fails to go to the suspended state upon the lid close anymore. I couldn't diagnose why.

On the other hand, suspending the laptop using systemd (systemctl suspend) works flawlessly. Not only the system goes into the standly correctly, it wakes up with the NetworkManager intact.

Therefore I suspect that this issue might be PowerDevil-specific.

Priority-wise I'll set it "Normal" for now, but it is between Normal and Major in my opinion, since the suspend-on-lid-close is crucial for laptops.

Thanks,
Vladimir