I'm not sure what the problem is,
it could be a system code specific, or a gesture recognition problem.
In case it is related to the gesture in windows 7 try to check the mouse properties :
-Go to the Start > Control Panel > Mouse
-Click on the Pointer Options tab
-Ensure that Display Pointer Trails, Smart Move, and Acceleration in Games options are disabled (some of these options may not be displayed, depending upon which version of Windows you are using)
-Exit the Mouse Properties window by clicking OK to save your changes
or :
-Open Control Panel > Hardware and Sound > Pen and Touch.
-In the menu that pops up, click the "Pen Options" tab at the top. A list of Pen Actions and their mouse equivalent should appear.
-Select "Press and Hold" and click "Settings..."
-Uncheck the box that says "Enable press and hold for right-clicking" and press "OK".
-Try to disable other options