I just had a look in my Sexcoin wallet version 4.8.4.
In the Debug - Console when I write 'help' I can see in the list that there is a command: settxfee
Could it be that in your wallet this command has been setup with a fee?
Just a shot in the fog..

..added later: oh I see - so when you receive SXC from another wallet (not another of your own wallets?) they have prob setup a fee in their wallet..