If the kernel is in the 2.4.20 or 2.4.21 series (and if the kernel mailing list is right, other versions as well) then it's quite possible it's the ACPI included in the kernel.
In my case sound would hang when I accessed the web.
Try booting with the kernel with acpi=off as an appended parameter. (at the lilo command prompt).
There is a fair number of discussions in this forum on the topic. Search on ACPI or nvnet.