[Plugin: Cart66 Lite :: WordPress Ecommerce] UTF8 encode – Portuguese

I had the same problem and I had to edit the core code.
Each time you find htmlentities in the code (only on 3 php files) you have to add a bit of code.
For example, in admin > products.php, you change: htmlentities($product->options_1)
into:
htmlentities($product->options_1, ENT_COMPAT | ENT_HTML401, "UTF-8")
Then no more accent problems… Of course you have to change it on every update.

I suggest that Reality66 adds it in its next update !