Thanks for your help Zuiko! 
I don't know if anyone else has experienced this problem before, but I'll describe it so that if anyone else runs into it they can read this and save them some time:
I have my SE/30s installed IIsi and IIfx ROM SIMM, following the instructions found on Gamba's page. I was able to boot into System 7.5.5 with 32-bit clean SIMM, but I noticed that whenever I go into the memory control panel on the SE/30 and restart, it causes a Sad Mac (see post above) and make the previously bootable drive unbootable! :disapprove: When I attach the drive into the my Power Mac 7200, it tells me the drive is unreadable and needs to be formatted!
Luckily, I had a DiskCopy image of the ResEdited System 7.5.5 and I reformatted the disk and copied over the image onto the freshly formatted disk. I then restarted the Power Mac using the ResEdited System 7.5.5 and turned off virtual memory and then restarted again.
Then I plugged the disk back into my SE/30 and it started up fine, restart, no more Sad Mac.
Now I can get onto the easy part and install more RAM. First I need to convince my wife...
I don't know if anyone else has experienced this problem before, but I'll describe it so that if anyone else runs into it they can read this and save them some time:
I have my SE/30s installed IIsi and IIfx ROM SIMM, following the instructions found on Gamba's page. I was able to boot into System 7.5.5 with 32-bit clean SIMM, but I noticed that whenever I go into the memory control panel on the SE/30 and restart, it causes a Sad Mac (see post above) and make the previously bootable drive unbootable! :disapprove: When I attach the drive into the my Power Mac 7200, it tells me the drive is unreadable and needs to be formatted!
Luckily, I had a DiskCopy image of the ResEdited System 7.5.5 and I reformatted the disk and copied over the image onto the freshly formatted disk. I then restarted the Power Mac using the ResEdited System 7.5.5 and turned off virtual memory and then restarted again.
Then I plugged the disk back into my SE/30 and it started up fine, restart, no more Sad Mac.
Now I can get onto the easy part and install more RAM. First I need to convince my wife...