No need to re-install - just boot without startup-sequence (if you're stuck in a crash loop then do this from a cold start, before the ROM update has a chance to kick in) and then rename the update file from the AmigaDOS shell. It's in Devs: and is called something like AmigaOSRomUpdate.
SetPatch calls the ROM update and if it can't find it (i.e., it's been renamed) it'll skip past it.
The ROM update has some compatibility problems with certain hardware that can cause crashes. If you want to get most of the functionality of the ROM update back, you can selectively skip certain modules that cause conflicts by using command line arguments on the SetPatch line in the startup-sequence. See the
OS3.9 FAQ.
Also, if you run one of those utility programs early in the startup-sequence to reserve memory for Mac emulation you can get rid of it. That functionality is built into the ROM update and running one of those programs AND the ROM update can cause the crash loop you described.
