HELP with ATI Tool!

When I increase the core clock frequency by 5mhz it just automatically goes back to the default speed. How do I stop this? I'm using ATI Tools 0.25 Beta 15. My card is the HIS X1950Pro 256mb. My power supply is this, if you need to know - nothing wrong with it -

http://www.ebuyer.com/UK/product/124926

Any help would be great, thanks.

You need to increase it more, there are like set clocks. For example, if the stock is 580, setting to 585 may not change anything, but setting to 590 might go up to the next clock..

See what happens when raising it further, and try going to the latest version of Ati Tool (0.27b I think)