I'm having a strange problem with my computer:?

[tim]

I don't know exactly how to describe it, but it's severely annoying to say the least. I will be typing in a web page, or any chat box, or on an online game, and suddenly (and frequently) my cursor will like "disappear" or change to a different window or something and I get that annoying windows "error" beep. I then have to click within the window or screen again to get my cursor back. No I didn't move my mouse outside the screen, no I didn't click anyplace else. It's just like the cursor goes away. Any insight as to what is causing this or how to fix it would be greatly appreciated. BTW, it happened 6 times while I was typing this message. I'm on a desktop computer running Vista 32. This problem started about 3 weeks ago with me making no changes to any hardware or software for months now (other than occasionally updating graphics driver) And no this didn't happen anywhere near that event. I've replaced my keyboard, and moved my mouse to different usb port, also cleaned optical lens on mouse. Any input would be appreciated, I'm out of ideas!!!!