mysqld fails to start at boot time only

[rudu <rudu@cegetel.net>]

Hi,
Running wheezy on my laptop.
I can glimpse while booting a message :
Starting MySQL database server: mysqld ...... Failed!

Indeed  a command "ps aux | grep mysql " at the end of the boot returns 
nothing.
But I can start it with "service mysql start" ok.

/var/log/mysql.err and mysql.log are empty.
dmesg | grep -i mysql    returns nothing

I'm at a loss here.
Anybody sees how I could get mysql to be fired up at boot time ?

TIA
Jean-Marc