Thanks for your answer, but the targets are in my firing arc and I don't get interrupted by anything. I've even tried things like using CSV or CRF concurrently or just activating the Spinal Cannons without any other weapons firing, yet nothing seems to do the trick. I'm really at my wits end here.
Do you get an error message? I also wanted to retrain today, but got the message "There was an error trying to reallocate your skills" or something along those lines. I bypassed the problem by resetting all of my skillpoints instead of just reallocating the ones I intended to.
The last time I did it a few hours ago there were romulan ships, but they took an awful lot of time to respawn. Since there may be a common source to these problems, I thought I'd mention it here.
I made the same experience. Activated the cloak as soon as I noticed the Tac Borg Cube was onto me, but a few moments later i blew up nonetheless. Same happened with spheres and other non-Borg enemies, they just kept firing.