imscp-backup-all access denied for mysql

Hello,
from 2 days i have on all of my servers:

iMSCP::Database::mysql::dumpdb: mysqldump: Got error: 1045: Access deniedfor user 'root'@'localhost' (using password: YES) when trying to connect

mysql password is the same. What can be the reason ?

Problem is in file /var/www/imscp/engine/backup/imscp-backup-imscp

my $rs = $db->dumpdb($main::imscpConfig{'DATABASE_NAME'}, $sqlFName);
error("Unable to dump the $main::imscpConfig{'DATABASE_NAME'} database") if $rs;
return $rs if $rs;

Somehow $rs returns 2.How can i make it print user and password so i can see what is the problem exactly ?

I put extra prints in: imscp-backup-imscp

function "sub _backupDatabase"

print "Date: $date\n";
print "SQLFileName: $sqlFName\n";
print "DB Host: $main::imscpConfig{'DATABASE_HOST'}\n";
print "DB name: $main::imscpConfig{'DATABASE_NAME'}\n";
print "DB User: $main::imscpConfig{'DATABASE_USER'}\n";
print "DB Pass: $main::imscpConfig{'DATABASE_PASSWORD'}\n";

Date: 2015.03.16-15-51
SQLFileName: /var/www/imscp/backups/ispcp-2015.03.16-15-51.sql
DB Host: localhost
DB name: ispcp
DB User: root
DB Pass: *********
RS = 2

Information is absolutely correct as in /etc/imscp/imscp.conf but
still the scripts exits here:
my $rs = $db->dumpdb($main::imscpConfig{'DATABASE_NAME'}, $sqlFName);
error("Unable to dump the $main::imscpConfig{'DATABASE_NAME'} database") if $rs;

[ERROR]

iMSCP::Database::mysql::dumpdb: mysqldump: Got error: 1045: Access denied for user 'root'@'localhost' (using password: YES) when trying to connect
main::_backupDatabase: Unable to dump the ispcp database

[FATAL]

Exit code: 2

Anyone can help ?

Additional info:
access denied i have only on machines which are upgraded from ispcp 1.0.7

Nothing which is non-standart.
I remember did apt-get update, apt-get upgrade.
3-4 new packages upgraded but nothing special i think.

Start-Date: 2015-03-15 12:33:42
Commandline: apt-get upgrade
Upgrade: libnss3:i386 (3.14.5-1+deb7u3, 3.14.5-1+deb7u4), libicu48:i386 (4.8.1.1-12+deb7u1, 4.8.1.1-12+deb7u2), libssh2-1-dev:i386 (1.4.2-1.1, 1.4.2-1.1+deb7u1), libgcrypt11-dev:i386 (1.5.0-5+deb7u2, 1.5.0-5+deb7u3), libssh2-1:i386 (1.4.2-1.1, 1.4.2-1.1+deb7u1), libgcrypt11:i386 (1.5.0-5+deb7u2, 1.5.0-5+deb7u3), gpgv:i386 (1.4.12-7+deb7u6, 1.4.12-7+deb7u7), libnss3-1d:i386 (3.14.5-1+deb7u3, 3.14.5-1+deb7u4), gnupg:i386 (1.4.12-7+deb7u6, 1.4.12-7+deb7u7)
End-Date: 2015-03-15 12:34:17

I can confirm after that date backups are not working. From WEB control panel is ok, everything works except backups for customers and imscp.

Peoblem fixed !
my.cnf had extra line for socket connection.
Thanks people.

.my.cnf should look like this:

[client]
user=root_mysql_user
password=mysql_passowrd
socket=/var/run/mysqld/mysqld.sock

socket line may be different or even missing
file should be in /root folder and readable/writable only by root !