This was a problem I had regularly on my "old" Gateway Pentium Pro 200, using Windows95, Prodigy Internet with Netscape 4.05.
As of March 1999, I switched to using a "generic" computer, Celeron 366 clocked to 450, Windows98, using same Internet servcie and browser, same version of UFT (whatever it was a year ago). I had this lockup with clicking the mouse only once on my newer computer. (Yes, I remember that one time because it startled me.)
Just thought I would toss this in to confuse the issue.