Without more information the best I can do is give you some general trouble shooting steps:
First, test it with only everquest running and see if the mouse works. That will demonstrate rather it is everquest causing your problem. Another step you can take is to see if the same mouse works on another computer with everquest. Also, you check your key board for stuck keys - or you maybe pressing a key without realizing it. I just did this myself - purchased a new orbweaver which has a space button I wasn't aware of and was using for a thumb rest - needless to say things acted a bit funny. Check to see that the touch pad is disabled they can cause conflicts with a mouse.