Hi,
I've just noticed that I can't change the settings in the quota manager extension once they are filled.
Precisely, I can change them but it doesn't change something for the uploader.

Zenphoto 1.4.5.7 [59c22b2fba]
MySQLi : 5.1.67
PHP : 5.3.22
encoding : fr_FR.UTF8
theme : lightly modified ZPskeleton

What exactly are you seeing. I have just tested this and the setting does change on the upload page if I change it for the user.

After having changed the settings, when I log as one of my user who has already exceeded his quota as set in the previous settings, it doesn't change the message saying that his quota has been exceeded.

Is it clear enough, Stephen ?

Not 100% clear, but I presume what you have done is to increase the user's upload limit.

Anyway, I am not seeing that. Check when you extend the limit that the new allowed value is in fact larger than the used value.