tax return delayed

Just a receive an email from the tax office stating my return ha been delayed. Not that uncommon i guess except for the fact i have not lived in Oz for 10 years and the only reason I filed a return was because bank interest recieve didn't have non-resident withholding taken from it. So i fronted up to pay the 39% (instead of 10%)... Otherwise no other income or dealings with Australia. So it's not and income/deduction story.

My return should have take a few minutes to do, so I am curious as to what the might be. Never had a delay in 20 years and this is simplest return i ever lodged.

Any ideas? Could it just be a residence test? To be sure I am a non-resident? I have no house, car, bills, etc in Oz and was only there 20 days on holidays in 2011/12.

Got me puzzled this one...