Why some types of ranked matches become unavailable?

Upon HotS release I played mostly 1x1 ranked games... at some point 1x1 got 'unavailable' for me. I resolved that by hitting 'back' button to escape matchmaking screen and coming back.

But in 1-2 weeks later the same happened and i can't escape this limitation anymore: whatever i did I was not able to start any 1x1 match.

Ok, I played some 2x2 games... few weeks later I was forced to play 3x3 or 4x4... or, i thought I understood the rules: you should play EACH match type...

But now, I have played 1x1, 2x2, 3x3.. and available are 2x2 and 4x4...

Why only certain types of games are available?

What is the rule here?

Like stated by tenfour, this is a know bug. Follow this link for an official blue post on solutions: http://us.battle.net/sc2/en/forum/topic/8796679671#2

Quote:

• 1) Reset your network.
• 2) Flush the DNS cache.
• 3) Delete the Variables.txt file from C:\Users\\Documents\StarCraft II
• 4) Delete the Battle.net cache.

As for myself, I simply log out and log-in again.