I have been tentative about this issue of freezing because I thought that it might be a Toshiba laptop issue. However, this is not the case because I have discovered that over the same period we have been discussing this, many people have been experiencing the same freezing on other laptops and desktops, see here and here.

It is not due to:
1. cpu temperature, because I have been monitoring my cpus with kima and the temperature rarely rises above 53 degrees C
2. a runaway process, because I have also started using the "runaway process catcher"
3. Opera, because it occurs with other browsers like Konqueror and Firefox, and even if no applications are running
4. Beagle, because I have removed all beagle rpms
5. acpi settings because I have tried many things, it even occurs with Failsafe mode

The issue seems to be related to using kdm and hardwired IP. It occurs with kdm & wifi but only rarely. It does not occur if xgm is used instead of kdm.