What is the Sixth Step of MacBook Repair? My Macbook has crashed once or twice daily ever since I installed Lion. I am unable to return to Snow Leopard because my Time Machine is now coupled with Lion.

I went through the sequence:


Reset the PRAM: Hold down Command ⌘+Option ⌥+P+R on boot. Release after hearing the computer chime twice. http://support.apple.com/kb/HT1379
Reset the SMC:
Shutdown. Disconnect power adapter. Remove the battery. Press and hold power for 5 seconds.
http://support.apple.com/kb/HT3964
Verify/Repair disk
Reboot into the recovery partition (press Option ⌥ while booting) and run Disk Utility. The disk had two problems, which are now fixed. http://support.apple.com/kb/HT1782
Run the hardware diagnostics:
Reboot with the original OS X Disk 1 while pressing D. The hardware diagnostics (memory only, apparently) says all is well. http://support.apple.com/kb/HT1509
Reinstall OS X from the recovery partition:
Hold Command ⌘+R while booting.
Slight reduction in the rate of crash (but that's only an impression). http://support.apple.com/kb/HT4718


What would you try next? 

Edit:
The machine is out of warranty and out of Apple care.
Take it to Apple and ask them to fix it under warranty.  If you have made a clean install, and can still demonstrate the problem, you almost certainly have some sort of hardware issue.

If you did a reinstall, then added something that has a kext, that might be responsible, though, so in the (unlikely) event, reinstall, don't install that, and see if that fixes the problem.