Hold Right-Click + "W" or "S" in Scene Editor not working properly!!

I have this really big issue and look around here for answer and also the web but no luck on my side.

::PROBLEM:: While Right-click + "W" & "S" key not properly working while at scene editor moving your view forward and back left "A" and right "D" is working as usual. What it does is cut-off the view from the bottom when moving forward and the top when moving back which limit the meshes that i can see in the editor. for example i make a terrain and try to move forward the bottom half will get cut off and when i move back the top half will do the same while the view(or cam movement) remains stationary.

::WHAT I DID:: I updated my video card and no luck. I un-installed unity, deleted all files and folder accept my saved game files and download a fresh one and still does the same. the "W"&"S" was working before just happened recently. I also re installed windows just for this because not viewing some part of the meshes gets really annoying. It worked! I applied the hot fix http://support.microsoft.com/kb/976038 but couple of hours later. Same bug which is disappointing. I uninstalled the hot fix and still the same bug exist.

My Comp: Windows 7(64bit), ATI HD 6850, AMD Phenom II 6 -Core, MSI 870A motherboard, OCZ 4GB Memory.

Sorry for making it long, what should I do to fix if anyone know. Please Help!

I have very recently got this issue and realised that I had changed from perspective to Isometric view accidentally. A quick click of the bottom of the view gizmo in the top right of the scene view and I was back to using wasd as normal.