Solved, thanks!

Also, what determines country size for the purposes of GDI? The wiki article does not address it. Is it total acreage? Networth?

I have already read that wiki article, it does not address my concerns. Every country (excluding the top 10) on my scores list, all 50 of them, cannot be either twice my size or half my size - Thus, I do not see the reason that I am getting the error.

Oh yes, some stats may help.

Basics
Government C
Land 2000
Tax Rate 35%
Net Income $144,000
Net Food 448
Money $260,000
Food 150,000
Oil 130,000
Turns 28
Turns Played 1048
Turns Stored 0
Technology
Military 92.19%
Medical 89.31%
Business 135.25%
Residential 138.11%
Agricultural 135.12%
Warfare 2.0748%
Military Strategy 113.77%
Weapons 118.48%
Industrial 121.64%
Spy 118.82%
SDI 29.73%
Structures
BPT 15
Enterprise Zones 200
Residences 200
Industrial Complexes 200
Military Bases 200
Research Labs 400
Farms 200
Oil Rigs 200
Unused 6
Military
Spies 14,000
Troops 38,000
Jets 26,000
Turrets 42,000
Tanks 7,400
Readiness 100%
Nuclear Missiles 0
Chemical Missiles 6
Cruise Missiles 4

This is my first time playing. I have a country on the primary server, where I am ranked 285th out of 562 countries. A few days ago, I successfully did spy ops and attacks against countries slightly above or below me in rank. However today, I cannot attack any. I spent a few minutes trying every country number visible on the 'Scores' page, excluding the top 10, (as a test) and constantly received the error "GDI authority will not let you attack this opponent!".

What is going on?

*EarthBear prowls through the forest, following the scent of the honeybees*