I often order stuff from the States and sometimes they just do not accept foreign debit or credit cards.
Ususally this is just do to programming in the software, since credit cards are universally accepted.
A few times I solved the problem by calling the company and giving them my credit card details over the phone.
If your company is not willing (or able) to do this, I would go ahead and send a cheque.
I have not done that personally, but my husband occassionally pays items from the States by cheque and never had a problem.