we detected network instability caused by a high number of nodes running old versions of the wallet.
If you are using a version older than 4.0.5, it'd be necessary to update as soon as possible. Downloads available at:
Pi Users can update entering the following script on the terminal (using ssh or keyboard+display):
wget -O - http://navcoin.org/files/update-navpi.sh | bash
A new update method will be soon offered for users who can't connect over ssh or using a display.