During the last boot-up your system hung for an improer CPU speed

[cpunew]

Hello
I've upgraded my CPU about three weeks ago. When I replaced the CPU with the new one, the system auto detected and auto-changed the CPU speed to 2800 MHZ.
The system would get hung quite often since then and starting today it even started to shut itself down. Then when I reboot, it takes me to BIOS and the message it reads "during the last boot-up your system hung for an improper CPU speed."
And the power supply smells like something's burning although I don't think the PS is the culprit for the system hangs and shutdown since I've tried changing the PS and still resulted in burning smell.

The upgraded CPU is Pentium 4 2.8 Northwood 2.8 GHZ.
The mb on computer is ASUS P4SP-MX.

In BIOS, the following info. is displayed:
CPU Speed 2800 MHz
CPU Frequency Multiple 21x
CPU External Frequency 133/33
Memory Frequency Auto
CPU Level 2 Cache Enabled

Any suggestions would be appreciated.