MacOS – What does it mean when I get a server failure when connecting to a router with DNS protocol

I'm currently attempting to debug a Super Duper startup problem where it takes between 10-15 seconds to start up on my machine when wireless/internet is turned on. I have communicated with Dave from Shirt Pocket who advised that Super Duper usually has a lag like this when there are network drives mounted on my machine (i.e. Super Duper would attempt to scan these resulting in the lag). When I turn wifi off, Super Duper starts up immediately.

I don't have any network drives mounted on my machine and so this has all been very mysterious.

Last night, I installed WireShark and tried to see if there's anything interesting going over the wire. I noticed that roughly around the time I start Super Duper up, I see the following in WireShark:

Source    | Destination | Protocol | Length | Info
----------------------------------------------------------------------------------
My IP     | Router IP   | DNS      | 66     | Standard query 0xd574 A System 
Router IP | My IP       | DNS      | 66     | Standard query 0xd574 Server Failure 

The server failure is usually returns between 10-20 seconds (hence the correlation with the Super Duper start up lag). The request from my machine to the router sometimes happens repeatedly (i.e. 2 or 3 times) before the notice of failure returns from the router.

I'm not very familiar with using WireShark and reading information off packets in this way (indeed, it's very odd that this is causing any issue with Super Duper at all given that it shouldn't be going out on the network to look for stuff as I don't have any network drives setup at all on my Mac) – my question here is: does anyone know what is happening here and why do I get a server failure from my router? Internet is working with no apparent issues.

In case it becomes relevant: this is on a 2012 MacBook Air with OSX 10.9.4 plus the latest versions of Super Duper and WireShark.