Error in mysql

hi all.
I have upgrated the vps and now I have the next error:

ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (111)

somebody know how could I fix that problem?
thanks.

Can you connect to the database using standard MySQL command line client?

this error appear when I try to connect with mysql -u root -p

Sounds like you some issue with MySQL itself.