Hi
I managed to solve my problem, but it's rather strange.
I had noticed that the thousands separator had a symbol for an unsupported character (this character: "�") :
So I edited my "locale frensh" file on my server to see what the character was for the thousands separator :
It was the code <U202F> for "Narrow No-Break Space". But strangely it wasn't recognized by my server. I replaced the code with a simple space and rebooted my server. This corrected the number display, but strangely enough, it also corrected my initial problem with notifications...