The symptoms you describe for your SE/30 very closely match those I'm experiencing with a Mac LC 575. The system hangs shortly after displaying the "Welcom to Macintosh" screen. Unlike yours, booting from a floppy on my machine does work and the hard drive can be readily read and written to, but without a floppy it will not boot. I initially suspected a hard drive problem and ordered a replacement on EBay, but while waiting I ran a fairly exhaustive series of diagnostic tests to include reinitializing the hard drive and installing a clean OS and trying to boot from a second SCSI device. Result was the same: no hardware problems found, yet I could not boot from any SCSI device Once the hard drive arrives, I'll retest and post resuls, but I wanted to post this in the even someone else encounters the problem. Other than this post, I have not found anything on the Internet that describes this type of failure.