If you have payment issues, it might be because Linden Labs has released a new payment plan that is a beta version (website). At least for me, none of my L$ purchases have gone through since the change. So what to do?
One way I have found very effective is to go to a Virwox automat inworld, and pay with a credit card. They allow at least Visa Electron and the most common credit cards. There is a list of locations at the website, but an easy one for all Rag Dollz fans is outside their store (SLurl). Through Virwox you can move money between game worlds (for example Giant grid, Spoton3d, etc). There is also a Paypal automat next to the VirWox one by Rag Dollz.