Steam Won't Launch - CMultifieldBlob(pSerialized)

Solution 1:

Just delete the clientregistry.blob in your Steam folder and nothing else, then launch Steam. Steam will just make a new clientregistry.blob.

Solution 2:

SOURCE: How should I reset the ClientRegistry.blob when needed?

This error is caused by a corrupted ClientRegistry.blob file. Most likely, Steam closed incorrectly. Either your computer crashed or the Steam process was killed before Steam finishing writing to the file.

One way to fix this error is by going to your Steam folder (following are common default locations)

• C:/Program Files/Steam on 32-bit Windows OS
• C:/Program Files (x86)/Steam on 64-bit Windows OS
• Users/[username]/Library/Application Support/Steam on Macs

For Windows OS, you'll want to delete everything EXCEPT steam.exe and the steamapps directory (this holds your game data). Then, restart Steam and you'll be fine.

For Mac OS, just delete everything in that directory and restart Steam.