I have experienced this problem with all sense roms using the #89 toast kernel for the hero(FreshRom, FreshToast, Aloysius, DamageControl, Hunnybun, etc), regardless of SetCPU/overclock widget settings. I even tried locking it at 245-245, or 518-518, and also 768-768.
I used darchstar's DarchDroid (v2.6.4/v2.6.5) for about 2 weeks overclocked to 768 with no FCs.
Im going to try 2 things.
***One is to try the old #65 kernel, which I think lacks BFS or compcache, or both, I don't recall which. See if that does anything.
***Also, I don't think its compatible, but I'm ballzy(crazy)(and don't know enough to know whether it will work without trying it), so I'm also going to try switching out for darch's kernel if the above doesn't work.
And if none of these works, I'll try going back to the HTC kernel =P
EDIT: PS, Has anyone be able to replicate this issue with the phone unlocked? So far I can only reproduce this if the phone is locked, it doesn't have to be asleep, just locked. I wonder if it could be a conflict of sorts with the HTC lockscreen, as darch's rom worked so great, but uses vanilla lock. I might have to flashed to the DEodexed version so get rid of the HTClockscreen, and see what happens =D