Thanks Teelk and Dioncecht for those information. No chance so far with the update.
First, I copied a fresh version of the 1.4.1 files on a test server, run the installation .script, deleted the newly created 1.4.1 database, uploaded my 1.4.0 database and tried to run the update .script. I got the following error message : "I am sorry, but your database type is not supported."
Then I tried to use the .script written by Dioncecht. Apart from some problems (my host does not allow to copy from one database to another), I finally could change a little the .script after copying all 1.4.0 tables with a temporary name (old_TABLENAME) in the same database as the 1.4.1 tables. But when I run the .script, I get on most of the tables the error "entry already exists". If I first empty the 1.4.1 tables, I obviously would loose data (for example, the new config table is larger than the 1.4.0 one)...
Any idea on how to proceed?
I am thinking of giving up the upgrade, as it seems that it will require too much troubles... I am afraid that if just copying the old database into the new one is co complicated, then adding all mods again might prove much too difficult...
Thanks for your help,
sanji