Android backups: MD5 checksum and other CWM Recovery errors

• MD5 checksum error
• Data corrupted
• No directory XYZ

Such error notices remind you of the fragility of existence: if digital data rots that quick, even more so do your analogue body, heart and soul. Yet let not all hope be lost.

•  The MD5 checksum error

Cause: The MD5 checksum file for the backup was generated under a different Android OS or configuration.
1. Remove the SD card and browse its content on another computer.
2. Delete the content of the *.MD5 file, to get an empty file. Just open it (e.g. in Notepad) and delete all. (Do not delete the file itself, though.)
3. Rename the CWM Recovery backup folders, removing the spaces in the folder names.
(Some CWM Recovery versions do not like spaces for some reason.)

•  System restore errors

Cause: The restore process modified the CMW application itself. 
1. Reboot your phone
2. Enter the CWM Recovery menu again.
(Yes, as simple as that)