OK: I spent a semester at Macquarie University but never heard the term "cubing" and it's not in my Dictionary of Australian Slang. Little help?
I was going to mention the knob on top of the spool as the exact same thing happened to a fella down here in Aust on his 14000 shperos.
He had a 100kg plus marlin on for one and a half hours no problems and then a couple weeks later he was cubing when his reel screamed of just like yours.
Same thing the plastic knob melted to the drag and ceased up.