Reporting the same thing, same symptoms on sse2 (dothan) machine:
-it seems that sse3 emu is not working since first release of legacy kernel for SnowLeo.
-distorted graphics
-safari hangs
-openGL and other sse3 software fails.
-the most annoying thing: system cannot umount disks successfully. (anyway manual umount from console works.)

I don't know if that matters - no HPET in my machine.
10.5.8 works almost fine with "avakov" kernel, but no OpenGl sse3 support anyway.
I think our older machines needs stable sse3emus, so serious revision of sse3emu code is required, there is something wrong inside.