Q: What's wrong with my mouse?

Of late I have been facing this problem: when the mouse is moved, the cursor moves, but clicking the mouse does not execute the required command! This problem stays around for brief periods and then the mouse begins to function normally. After repeated complaints made, the technician finally replaced the mouse I guess 2 weeks ago. The problem seemed to have gone away but today, it has recurred. This is a very annoying situation. Can any one let me know what the problem could be? I have just contacted the technician who opined that it could be an OS problem and had asked me to open a new account. I have my Mac covered anyway for and is under guarantee,however is an OS problem a serious one? What is the exact use of opening a new account and is it necesary for me to do it?

Thanks in advance.