The most useful info appears to be in this Reuters article.
Exclusive: Radar data suggests missing Malaysia plane deliberately flown way off course - sources | Reuters
This Time of India report is also relevant
Radar suggests missing Malaysian jet changed its course more than once - The Times of India
The relevant Malaysian military radar sites appear to be at Kota Bharu and Butterworth.
MH 370 is reported now to have been routing between named waypoints. Your most likely options are:
1) it was detected on military radar, but not deemed a threat due to its routing, and therefore not investigated.
2) it was detected, deemed a threat but not identified.
3) it was not detected, or not detected often enough to generate a reliable track
All of the reasons for the above would make the Malaysian authorities look bad. Questions might include:
What was the system serviceability and effective coverage?
Was this an operator or command cock-up?
Do they co-ordinate with the civilians, including flight plans?
Do their systems include transponder codes?
Do they have an effective Quick Reaction Alert?
I suspect the details are coming out now because they are reviewing the radar recordings but only now realise what they need to look for.
My best guess is that they routinely ignore civilian traffic routing between named waypoints. They will absolutely not wish to admit this, especially if it is known that they do so, as whoever was flying the jet may have planned for this.