check this out
I have solved my problem with "still waiting for root device." I had been rolling back AppleACPIPlatform.kext and IOPCIFamily.kext to version 10.6.7, which is what I needed to do to get Lion to boot up properly. However, the 10.6.7 versions don't work with ML. When I used the 10.7 versions of those 2 kexts, it found my boot drive. Now, I am getting stuck at "waiting for DSMOS." I'm sure there is some kext that also requires a roll-back. I will ask for suggestions and report my progress at this stage in a new thread once I have read what others who have gotten stuck at this stage have found to work. Thanks.