NetScroll+ Optical ps/2 mouse worked in 4.7 but not in 5.1

My Genius NetScroll+ PS/2 optical mouse was working fine in the console, and in KDE, with FreeBSD 4.7, but is working erratically in the newly installed FreeBSD 5.1 console, and on the new KDE 3.1 Desktop.
During installation of 5.1, with port as /dev/psm0, protocol as 'auto', and while testing the mouse daemon, the pointer was initially difficult to see and then, with mouse movement, appeared as if delayed by about 3 seconds, but did seem to move to a reasonable position. 
After successful installation of 5.1, the mouse cursor behavior is the same as during the installation's test configuration, and it's behavior on the console is similar to its behavior in KDE 3.1.
While moving, the pointer disappears, and then it re-appears when the mouse is stationary. It doesn't seem to copy or paste in the console, but left-clicking in KDE does seem to work, if I can position the cursor over a button, and right-clicking does work over the KDEE desktop.
Thanks for any clues.