I got this strange error the other day after being disconnected from Steam. I was like WTF, seriously, WTF. Anyway I found a solution to this error thanks to a thread from Fuel. So if you happen to have such an error, here’s what you need to do to fix it.
Navigate here: c:\program files\steam and delete the clientregistry.blob file. Apparently the file will be automatically regenerated and after restarting Steam, everything will be fine. So if you ever happen to come across a strange error such as: CmultiFieldBlog(pSerialized):Bad field – exte past end of blob, have no fear, there is a solution. Happy Holidays!