With Visa Electron cards I beleive that you have to have your card set up to allow international transactions. If you haven't done this then that may be why your transactions are not working when trying to buy L$. I suggest you contact the card issuer and ask them if it is possible to arrange for international transactions.
Otherwise, LL have a billing service which you can contact -
Long distance ( not free, but you can use Skype to save some cost ) : 703-286-6277
**Note: Support is offered only in English