brief, intermittant freeze of cursor

openSuse 11.4 (32-bit with updates on 64-bit hardware), KDE on a Toshiba Satellite laptop, external USB mouse. The touchpad is turned off with the button on the keyboard (it works, have not used it enough to notice freezing).
Cursor freezes for a short time, from a few seconds to about 10 seconds. Can happen many times in a minute, just a few seconds apart. This behavior is new in the past few weeks, but getting worse. Have had 11.4 installed since shortly after it came out.
Have not been able to see anything in System Monitor to indicate what might be hogging CPU cycles. “top” puts Firefox-bin at the top, but with only a 7% or 10%CPU; other freezes see Xorg at the highest %CPU, but less than 10%.
Suggestions welcome.