Hi,
I found that the language string for the "Add" button is using the back-end one instead of the front-end for non-options products.
To fix this, please go to "[kartris folder]\UserControls\General\AddToBasket.ascx" Line# 17, replace the word "_Kartris" by "Products" save your changes and that should do the fix, so the whole line should be:
<asp:Button ID="btnAdd" runat="server" Text='<%$ Resources: Products, FormButton_Add %>' CssClass="button" />
Will apply this fix into the next release.
Thank you,