Have you tried to use setcpu? Maybe system panel lite is reporting the speed incorrectly and something else is causing the lag. So far, it looks like you've only used CM7 to change the clock speeds. You can get setcpu for free from the XDA forums. Also, try different governors. That might help. Are you using the rom's default kernel or flashing a new kernel over it?
I've never seen this type of bug. If it were a hardware bug, temperature would be the only reasonable explanation for the 5 min delay before it sets in, and even then, heat issues usually cause a lockup. Otherwise, a hardware flaw would cause the phone to not boot or for the clock to be stuck always.
I've never seen this type of bug. If it were a hardware bug, temperature would be the only reasonable explanation for the 5 min delay before it sets in, and even then, heat issues usually cause a lockup. Otherwise, a hardware flaw would cause the phone to not boot or for the clock to be stuck always.