My CPU has 14X multiplier. I cannot get it to stay above 10X. WHY?---& HOW do I fix this?

Hi-
When I set my CPU to optimized defaults in the Bios, Its frequency is correct at about 2630 mhz. However for some unknown reason, it eventually drops to a 5X multiplier (or about 1020mhz) and it stays there even after rebooting. When I use a 3rd party tool to boost it, it crashes if I try to go above 10x/11x multiplier or 2000mhz. I cannot get it to the default 14X multiplier without it freezing up.

I do not like to use the the bios default method (wihich works for a while) because it changes all my other manual settings as well. I have older AMDs @ 1000mhz that perform way better than this @1000mhz. At the correct 2.6 ghz however, this thing is really a beast. Can someone help me keep it that way?

Can anyone tell me why the PC does this and what I need to do to prevent it from happening?

CPU is AMD 64 x2 5200 rated at 2.6 GHZ on a home made PC with 3072 MB ram. MB is a MSI K9VGM-V with a VIA KM890 Chipset. I am not a beginner on this topic, but I am in NO WAY near being an expert. I am just a notch above beginner in this area of computing.

This is my 1st post here, Ever.

Thank you in advance,
Donnie616