Hello Ive been getting this error but it usally happens when I am departing. It really sucks cause sometimes I have no freken clue where the aircraft is, cause it removes them from my session. But towards the end of a flight they may reappear. Im just scared im going to nail someone lol. Take a look at the pic below please

I see the McAfee sheild on your taskbar, try shutting McAfee down. I could not even make SBRelay connect when I got my Dell that came with McAfee. AVG makes a good free for home use anti-vuris program, that works with FS with no problems