With fear of what will happen with the upcoming BIP 91 activation, big bitcoin players like ShapeShift.io and Coinbase are pausing to all transactions to "see what happens." With block 477,120 marking the activation of BIP 91, theoretically blocks will be rejected that do not support the SegWit (short for Segregated Witnesses).
It would be a good idea to make sure your bitcoins are secured in a cold wallet during blockchain changes like this. We will know soon enough how BIP 91 affects us, but meanwhile, avoiding transactions before the activation block is a good idea.