Save contribution amounts page gives error "Please enter a valid money value (e.g. € 99.99)."

I've created a civi contribution page to accept donations. I entered in some default amounts (10.00, 20.00) etc. It all worked fine.

Then I went to edit the contribution amounts form and when loaded the amounts fields contained the values "€ 10.00", "€ 20.00" and so on. Saving the form without removing these extra € gives the error "Please enter a valid money value (e.g. € 99.99)."

I don't remember this happening with 4.1.5.