Modifications are currently being made to the Infura network. Infura is essentially a series of nodes sitting behind a load balancer. This is what our Lightwallet runs on. While modifications are behind made there is a rare occasion that nodes get out of synch, and this is why your transaction is "Pending". While these modifications are taking place trying the transaction again after a few minutes solves the issue.
You can click on the "Transaction History" icon to the right of your Ethereum address. Then click on the "TX Hash", it shows your transaction on the Ethereum network. If etherscan shows an empty TX Hash, or no transaction at all, this means that Infura got the request to send, gave you a TX Hash, but didn't broadcast it to the Ethereum network because it was out of synch. As I mentioned, trying the transaction again should work.