Linden Lab Official:I paid US$ for something, but the system doesn't seem to know it yet.
There are a few things related to Second Life that you need to pay for using US$. These things include:
When you've bought these items, you should be able to use them more or less instantly.
When something like your land fees are due, the charge is applied to your account. It may show as a negative balance until the next day, because the system hasn't processed it yet. In most cases, the charge is applied overnight in the form of payment on file.
If you're having problems that seem to indicate the system doesn't realize that you've paid for something, you should file a support ticket.