Could not open file "pg_clog/0000": No such file or directory
If pg_clog is gone..... thats bad, this stores the commit log so the database knows what has and has not been committed.  I would start looking at backups now, or if the data is disposable and there is no backup then building a new cluster.  There are ways you can get the data out, but as far as I know they are very time consuming.

The bigger question though is what happened to your machine to cause this?