Either your HDD/SSD has failed or the partition or RDB has become corrupted. I'm afraid that you'll have to try to recover your files to somewhere else, reformat and reinstall MorphOS.

While it is possible that an app could have caused this, it is vanishingly unlikely. I guess your filesystem could have been corrupt for a while, and extra activity has pushed it over the edge. Or it's a physical device failure, in which case the new install will just become corrupt after a time too - or completely fail to reformat.