I've experienced a simular problem... how ever it happened with all software which gets things from the internet.... not just FFXP. 
 
I worked out the problem was something to do with my ISP and the solution was to have 2 threads of anything running at once.. that fixed it for me. 
 
So basically have FFXP open and something else downloading, or just 2 instances of FFXP (Transfering though, NOT idle)
		 
		
		
		
		
		
		
		
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