I installed the newest ISO for ESX 3.5 (2/20/2008) on an IBM x300 that had ESX 3.0.1 on it as a test machine. I first tried an inplace upgrade and it said it completed. I rebooted and after a few seconds it gave an error "Error mounting root. Dropping to basic maintenance shell".
I then proceeded to try a fresh install. I am getting the same error!
Any ideas?