It sounds like the button action for your mouse are out of wack.
Open Control Panel by pressing <ctrl><esc> to bring up the Start menu. Type Control Panel in the run box. Once control panel is up use the cursor arrows to select the mouse and press enter. This will bring up the mouse settings. If you can't click on the Buttons tab, use the TAB to get there. Clear the check box labeled "Switch primary and secondary buttons". See if that doesn't get things working again.