Sounds like you have a bad mouse. Microsoft keyboards and mice most always work well with a Microsoft OS.
Check Device Manager and see what it says your mouse is.
Also, check to see if you have other mouse drivers loaded on your computer, if you do remove them.
I recently purchased the microsoft wireless desktop set.
Wireless Comfort Edition
Wireless comfort keyboard 1.0
Wireless optical mouse 2.0
The keyboard has been excellent. The mouse on the other hand is a different tail. I have updated the mouse drivers. I have also Tried to contact microsoft both via phone and email with no help. The email did not work because they don't have my model on the hardware list? Strange but okay. The left click works when it wants. I have tested the right click and mouse movement with no problems. The left click will work after about three times of pressing it. What I want to know is anybody else encountering this problem with any of the new wireless mice available from microsoft or did I get a bad pick.