I have had multiple incidents today of my glass fiber cables vanishing. There were a couple of other people that were on when i was that had the same problem. Someone in the lobby said there was a glitch with them, just wanted to make sure everyone was informed. I am not sure if this happens to everyone and in every server but it happened to me on north.
It's a problem with the Mod IC2 itself. I have done lots and lots of testing and debugging to try and solve it myself, unfortunately it's in the core of the mod and can't be fixed permanently. The problem happens with the unloading of the chunk that they are in but also in conflict with another item (typically a chunk loader) that 'resets' their 'connection ID'. Thank you for the report.