It's probably mis-identifying change outputs as part of the tx. Be sure to click on the thing in the bottom-right that says "Click to show tx info" (or something like that). it will show you a full list of inputs and outputs, with the wallet IDs next to them. My guess is that you will see 6.4999 in inputs from wallet X, and then 1.4999 BTC in outputs going back to wallet X. Then there will be a 5 BTC output going to the expected address.
We noted in 0.90 some issues with identification of change outputs, etc, and we attempted to resolve in 0.91, but the algorithm isn't perfect.
Where is that bottom-right thing that says "Click to show tx info"? In what window? Main window? Wallet window? Send window?