Here's another thing you can try. If I were to guess, I would think that the server you're connecting to is probably not giving you the correct information.

Go to Classic GUI by selecting it from the 'View' menu, if you're using the Lite GUI.

Then in the lower right corner of the screen in the Classic GUI, you should see a green dot. Press the green dot. This will bring up a list of servers to connect to. Try connecting to different servers and see if they show you the same total balance.