After reading the ReadMe that came with MRJ 2.2.5, the only thing I can think of is that you might be running into the problem mentioned here:
"MRJ 2.2.5 can only be installed in a disk or partition which contains a Mac OS 8 or 9 System Folder. If you are installing on a system that has both Mac OS 8 or 9 and Mac OS X disks or partitions, the installer may default to the Mac OS X partition. If this happens, use the ?Switch Disk? button to select a Mac OS 8 or 9 system disk on which to install MRJ."
If that isn't it, then maybe MRJ needs something like CarbonLib or some other extension that you might have deleted?