mouse help on Mac book pro

I have a new 17" mac book pro and sometimes when it starts up the mouse will not work on a regular left click, but a two finger right click on the mouse pad works and then I have to use the arrows and click on return to do something, sometimes if I relaunch finder a few times it will work right again, or sometimes I have to reboot a few times and then it will work, I checked for viruses and nothing, it is only about 4 months old, any help is greatly appreciated...