I went into my CCC overdrive panel, enabled it, and then restored defaults, and clicked apply at startup. This seemed to work the next couple times (3) I loaded SH4. Though as i said, its random so ill be monitoring it.
I cant use the ATT overclocking because the support for x1950xtx is limited. Otherwise id make a profile to force it into the right clock speeds.
I dont know if the latest Nvidia cards work the same way. The last Nvidia poo i had was the 6600GT which I had manually set higher by default anyhow.