Was this BIOS version "ww"?
I went through this my self with a friends KT7-RAID motherboard when I updated his to the latest BIOS version. It also wouldn't boot and would make a long beep when turned on then it would shut down. Well in the long run it turns out that there is a feature in the "WW" version of the bios that will shutdown the whole computer in 10sec if the fan attached to the CPU fan header is under 2000rpm. If you have no fan attached to that header at all it won't boot. I believe this might be what your seeing. Here is the readme from that bios version, you must read these carefully:
"And with this bios, the KT7 series FAN1 header must have the CPU fan connected onto it. If there is no CPU fan connect onto this FAN1 header or connect incorrectly, the motherboard power will automaticallyshutdown. This design protect the processor from damage by heat."
Good luck, ex.