There is a problem if we call sfPropel::getDefaultCulture() before doing anything else with propel.
Indeed, in this case, sfPropel hasn't been initialized and it doesn't return the same value after we have done any query for example (because before any query, propel is initialized).
So the method getDefaultCulture() should check that the class have been initialized or maybe you should transform sfPropel into a singleton ... i don't know.
I have detected this bug while using i18n tables in propel with the admin generator.
And with an admin-generated module on class model Article, if I set sf_culture to "fr", when I create an article, the title is stored into "en" culture, and the content is stored into "fr" culture.
I have encountered this bug into 1.1 dev version of symfony.