...for destroying one of my BO. Suddenly I couldnt replace powers on her because it said an unknown node hindered that from happen. So I had to discharge that BO and buy a new one and train that one up to Lt Cmdr and buy all powers again. Thanks for that. Seriously, I hope this wont happen again!
If this was Aceton Field, that bug had been fixed in today's patch. In fact, I personally can confirm it was fixed, because I trained over Aceton Field (replaced it with another skill).
For reference, Aceton Field is a space skill that was formerly flagged as a ground skill, leading it to be recognised in-game as 'Unknown Node' and otherwise unusable. This has been fixed in today's patch.