It may be because the new builds are defaulted at 710mhz. Give me a minute and I'll pull the 0913 build apart and swap out the boot.img so it boots at 600mhz
In the mean time, Try this build. You may have a "Lazy" Ascend. This is BobZ's CM 7.1 672mhz build.
CM7.1RC1-Ascend-BobZ672-070811.zip