Wireless Network Switch from Secured to Unsecured Automatically

Hi everyone.  When connected to my wireless network via my FIOS router (model MI424WRI) I notice that my laptop will randomly switch from a secured version of my wireless network to an unsecured version of the same network.  There is only one version of the wireless network listed (secured) when I view all available networks. This random switch usually results in my work VPN kicking off and then I need to restart the laptop to get the VPN working again. Why does this random switch from secured to unsecured (and reverse) happen, and how do I stop this from happening? Thank you!