Okay man! Thanks for your feedback. I've tried 25k and 50k without no luck...it goes up to 350k super fast...
I'll try with higher values of diff to see if something changes!
The usual minimum value is about 5000.
25000 isn't a low difficulty so it should have been accepted by the pool.
But didn't you write it like this: wallet.25K instead of wallet.25000 ?
Only numbers (with numerical characters) are accepted.