This error can often be caused by a corrupt 'ClientRegistry.blob' file, typically because Steam unexpectedly closed. This is often due to a crash or because the Steam.exe process was killed before Steam finished writing to the file.
Some instances of this error can be avoided by allowing Steam to fully exit, by clicking Steam > Exit or by right-clicking on the Steam icon in the System tray and clicking Exit, rather than forcing the process to end.
To fix this error please use the following steps:
- Exit Steam
- Navigate to your Steam installation directory (C:\Program Files\Steam\)
- Delete everything in that directory EXCEPT the 'steam.exe' file and 'steamapps' directory (all of Steam's game files are kept here)
- Restart Steam to test the issue