Please see this thread, from the lm-sensors mailing list: http://lists.lm-sensors.org/pipermail/lm-sensors/2006-April/015962.html (keywords for bugzilla: Asus P4S333 asb100 sis96x smbus quirk missing device)
This looks incredibly fragile. I think the easiest way to fix this is to explicitly call the 96x quirk from the 503 quirk after enabling the hidden device.
Created attachment 128338 [details] [PATCH 2.6.17-rc3] I2C: sis96x SMBus quirks cannot rely on link ordering I sent this patch upstream here: http://lists.lm-sensors.org/pipermail/lm-sensors/2006-April/016011.html
Any idea why this used to work for years and breaks now on FC4?
How was it fixed? Was Mark's proposed patch simply applied? I still would like to understand how the problem only ever showed on FC4.