Overclocking AMD Athlon XP 2400+ on A7V266-MX

Friends,
I have an Asus A7V266-MX motherboard with AMD Athlon(tm) XP 2400+ processor, 128+256 DDR RAM, 40 GB ATA HDD. It is running on Windows Xp Media Center and Redhat Linux. For the last 3 years, it worked cool @2000MHz in 133.33MHz CPU external frequency (DPI SW1 2,4 is ON).
A few days ago my CPU is automatically reboot and gave an error message that "some files are missing or currepted". I had found that my CPU is overclocking and its current speed is @2266MHz.
I had tried to trouble shoot it by Updating my BIOS to the latest Revision 1003 dated 14/09/2004 but it didn't solve my problem. Then I Change the CPU external frequency to 100MHz. (DPI SW1 2,4 is OFF).
Now my CPU is booting but it shows only 1700MHz. Asus Pc Probe monitor summary shows all are Ok!. Both my Motherboard and Processor are in the warranty period (only a few months remaining).
Is it the problem of my motherboard? Because I believe that the Bus Clock is increased by 2 (earlier it is 15 and now 17 ie, 133.33*15=2000, 133.33*17=2266 and 100*17=1700). If so, Please suggest me, what should I do to solve this problem?