Starting Server.... (Stuck and never loads)

Hi Guys, I have been reading your forums for a while. I have just started having a problem within the last week or so. I have two PCs with Terraria and my Son and or both my sons often play together. But in the last week or so when we Host and Play to set up a server after selecting the char and world it just sits at the Starting Server... screen and never goes any further. This is a non modded game, we have never loaded any mods previously.

I have googled and there seems to be a few...

Starting Server.... (Stuck and never loads)