Apparently, rolling back the IOPCIFamily.kext to 10.6.7, which is one of the kexts I need to roll back to install Lion, is what is causing the problems which are leading up to the "still waiting for root device" error. However, with my hardware (Dell Inspiron 1720 with X3100 graphics) I cannot get the installation disk to boot with the current version of AppleACPIPlatform.kext and IOPCIFamily.kext. So basically, I traded one problem for another.
do u have the _UID, Zero under Device (PCI0) ?? (dell laptop specific dsdt issue)
also with my 1520 i noticed past 2gb for install gave me issues for lion... and currently im having a hard time with 10.6.8 and x3100 version 1520
10.6.7 works fine.. 10.6.8 doesnt.. seems its the IOPCIFamily
almost everything from DSDT thread for m1530 applies.. its more like m1330 if u look for MECI and compare m1330 and m1530 and insp 1720 youll see m1330 matches almost complete (minus lan and SDcard locations in PCIE .. addresses change)