When I put in the device "wlan0" which is my active device, I receive the following error: "Xfce4-Netload-Plugin: Error in initalizing: Interface was not found."(sic) This is repeatable for eth0 as well. I tried using /dev/wlan0 as well to no avail. An interesting observation: when I hover over the applet while the error dialog is up, the "popup text" I guess you would call it says "wlan" without any 0, so maybe the applet is garbling the device field in the preferences. Also I might mention that the correct spelling is "initializing". Strangely, after trying multiple times it just started working for no apparent reason while I was filling out this bug report...
I am also seeing this bug. I just installed the netload plugin on Fedora 15, and I tried eth0 and a few other things, but it gave me the same error every time. I didn't have it magically go away. If you need more information, I'm happy to give it to you.
Don't think this bug is reproducible anymore so was probably fixed meanwhile?
the interface is looked up in if_nameindex(). http://linux.die.net/man/3/if_nameindex if it isn't found there is nothing to do, all the user can do is compare the name with the output of 'ifconfig' or 'ip addr show'. nothing wrong in the plugin. regards, mike