A lot of the time in my Career save, randomly all of my vessels lose their connection and I can no longer launch unmanned vessels - they have no connection even at the launch pad.
Logs just show errors like this (output and ksp.log respectfully):
ArgumentOutOfRangeException: Argument is out of range.
Parameter name: index
at System.Collections.Generic.List`1[System.String].get_Item (Int32 index) [0x00000] in <filename unknown>:0
at PartModule.ApplyUpgradeNode (System.Collecti
@_Augustus_ I get this too, be reassured you are not alone (BTW, I was once an active telescope maker - great stuff).
It happens apparently randomly after about 2 to 20 hours of playing and I have not been able to determine steps to reproduce. The entire commnet just suddenly goes down. It has been happening for some months and it still happens.
All unmanned vessels become uncontrollable and all comms lines disappear from both the map view and Commnet: Network in the tracking station v