It sounds like your screen updates are getting lost. This could be due to a flaky wireless link.
First thing to try is attempt to force a screen refresh on your remote viewer client (the machine you're sitting at -- look around in the remote viewer menus for a "refresh screen" action). Try it a few times; if it works, you should get a freeze-frame update of the remote desktop (your test, minimizing or maximizing one window, is perfect for this).
Second thing to try, particularly if the above works, is connecting the laptop to a wired network connection instead of the wireless. Does the remote screen refresh normally?
If it works on the wired network, your wireless signal is having problems. Does it work better on the wireless when you move the laptop closer to the access point?
Potential wireless trouble spots: Is the signal strong enough? Are you getting interference from neighboring devices? (Your neighbor's wireless, your cell phone's bluetooth, your kitchen's microwave, your house's water pipes?)