System won't go into Standby

[coffent]

I have a Jetway/Kuroshio BI-600 motherboard which has been working fine since I got it a little over a year ago. Suddenly, however, it has stopped putting the system into standby. If I tell Windows XP to go into standby, I get the normal screen saying "Preparing to standby", the monitors go into standby and I think the hard drives do likewise. However all the system fans keep running, and all 6 indicator LEDs on the motherboard remain on, indicating the CPU is still in full-power mode. If I momentarily push the power-on button everything comes back on as it should. Any thoughts as to what could be causing the problem?

[coffent]

I got a suggestion from Jetway to change the ACPI Suspend Type to S3(STR). I don't know how the BIOS setting got changed in the first place, but setting it to their recommendation fixed the problem.