I've managed to correct the problem, I explain how I got rid of it, in case someone stumbles upon this error.
The error wasn't possible to locate most probably because my SQL ODBC Driver was outdated/missing. I was still able to write in the database, but the error indentification wasn't correct anymore.
I upgraded the SQL ODBC Driver to mySQL 5.3 and was then able to locate the problem: Two of the parameters took the value NaN returned by LabView but which is not interpreted by SQL so it was truncated in the command...
