My mouse keeps disappearing what do i do to fix it?

Sometimes (once or twice a day sometimes more) my mouse disappears. I have to close everything in my browser for it to come back. It only happens when i have another tab open (idk if this is coincidence or not). It only disappears in the browser. I can still see it on the bottom bar (idk the official name for the bottom bar (the one with the start button :))) and on the desktop. i have a wireless mouse my computer is a compaq presario c500 and my OS is windows vista.