Site-dependent Frequency With Mouse Scrolling

I had previously (yesterday) asked a question about why using my mouse scroll wheel was causing a sound to emanate from my speakers. The thread is here:

http://cr4.globalspec.com/thread/44421/Why-Do-I-Get-a-Buzzing-Sound-From-My-Speakers-When-Using-the-Mouse-Scroll-Wheel

I am reposting because of the lack of interest/not-knowing-a-solution in the original post, compounded by the fact that no one (except for NotUrOrdinaryJoe) would be alerted by email because of the same.

Since I posted that question, I have found out the following:

• This phenomenon only happens when I am in Internet Explorer, Opera, or Outlook - no other programs.
• The frequency coming from the speakers is different for some sites in both Opera or IE; I have not been able to establish a correlation.
• For the same internet site, Opera and IE do not output the same frequency.
• In Outlook, it only happens when scrolling the preview window. Depending on the content shown in the preview window, the frequency varies.
• My optical mouse does have capacitors - 2 x 10uF Ecaps and 1 disc cap (value unknown).
• Changing to a different optical mouse gave no discernable change in the phenomenon.
• I had a power cord very close to the volume control of my powered speaker system. When I removed the power cord from the vicinity, I could tell no difference in the effect - frequency OR volume.

Sorry to be so lengthy and detailed but the force helping is not.

But, my curiosity is piqued! Help it I cannot. All and any input is welcome. (Even from DVader1000).

I am opening this as a discussion; feedback will be answered.

Mike