It's an eerie coincidence that the incident involving the MAS B777 and the QF A330 both occurred on the same route (although the aircraft were travelling in opposite directions to one another) and implicated ADIRU failures on both occasions.
The ATSB analysis of the B777 incident determined that:
The incident was triggered by a second accelerometer failure in the
aircraft's air data inertial reference unit (ADIRU). This unit is designed
to be highly redundant and fault-tolerant but the first failed
accelerometer's failure mode was not one that had been anticipated during
unit design and development. (It had been assumed that a failure would
always result in zero voltage output, but this failed device was producing a
high output value.) The twin failures exposed a latent software fault, which
resulted in the unit feeding incorrect aircraft acceleration data to other
flight control systems.
Boeing B777-200 aircraft first entered service in 1995 and this is the first
reported instance of the particular software fault, which was apparently
present in the unit's original design, affecting operation of an aircraft.
The incident highlights the fact that software testing can never eliminate
all risk.
What exactly happened in the case of the A330 we will find out in due course. The high degree of redundancy built into aircraft electronic hardware and software creates complexity that may be beyond the capacity of its designers to fully comprehend. It can also harbour defects that, as in the case of the B777, take years to manifest themselves.