Wenn a universal cable is switched off by a redstone signal and then switched back on, it does not connect properly. That means it visually connects but energy does not flow.
After relogin, the connection works. This can easyly be reproduced by connecting a full and an empty energy cube with a couple of universal cables. The a lever switches off one of them. After switching back on, no energy flows.
Mechanical pipes show a similar behavior.

Just fixed this in development branch, it'll be in 7.1 which should release in the next few days.