So I installed Mountain Lion but the error persists so the disk (or both disks) have been corrupted.
This is what the log says:
jnl: disk4: open: journal magic is bad (0x0 != 0x4a4e4c78)
hfs: late jnl init: failed to open/create the journal (retval 0).
hfs(3): Journal replay fail. Writing lastMountVersion as FSK!
hfs_mounthfsplus: hfs_late_journal_init returned (0)
hfs_mounthfsplus: encountered errorr (22)
hfs_mountfs: encountered failure 22
hfs_mount: hfs_mountfs returned 22
jnl: disk4: is_clean: journal magic is bad (0x0 != 0x4a4e4c78)
hfs: late journal init: volume on disk4 is read-only and journal is dirty. Can not mount volume.
hfs_mounthfsplus: hfs_late_journal_init returned (22)
hfs_mounthfsplus: encountered errorr (22)
hfs_mountfs: encountered failure 22
hfs_mount: hfs_mountfs returned 22
jnl: disk4: open: journal magic is bad (0x0 != 0x4a4e4c78)
hfs: late jnl init: failed to open/create the journal (retval 0).
hfs(3): Journal replay fail. Writing lastMountVersion as FSK!
hfs_mounthfsplus: hfs_late_journal_init returned (0)
hfs_mounthfsplus: encountered errorr (22)
hfs_mountfs: encountered failure 22
hfs_mount: hfs_mountfs returned 22
I don't really know what to do... Try to recover the data with possiblie data loss and getting all file names screwed up or wait for a fix from Apple. Using "first aid" or some external tool? This is a nightmare scenario...