The 6th level curse

I feel like I have been cursed. I have been at or around 6th level a handful of times, and each time the campaign has dissolved, and been replaced by a new 1st level campaign. Some examples:

K'rrul - My 1st character ever, a Kobold Rogue/Invisible Blade managed to just get into 7th level before our campaign ended. Even that was kind of a gimme, as the campaign had fallen apart once at around 5-6th level, and had picked up again, only to be destroyed again.

Haggar - Halfling Paladin. Made it to around 5th before that campaign ended.

Some wizard - I don't even remember his name. Red Hand of Doom, we got to 5th-6th levels and the campaign ended.

Klaus - Human Cleric of the Sovereign Host. Possibly my most enjoyable character. Just made it to 7th when we lost at D&D and the campaign ended.

Therryk - Dragonborn Paladin of Erathis. This current campaign has this cloud of doom hanging over it. Spotty attendance and disinterest seems to be bringing it to a close. Therryk is currently 6th level. We will see how many sessions we can get through before the curse ends us.

The thing is, each of these endings were big. Not just a change of DM, most of them involved 2 or 3 people leaving the group. I am guessing this next explosion will be the same. Some people will leave, and we will start over again. Maybe 1st level, maybe 4th level, but we will not get much past 6th level before the curse strikes. I'd like to point the finger and say that none of these were my fault. After all, *I* didn't leave, I'm right here. But perhaps this pattern shows that I do have a problem. Me and the surviving core of the main group, currently three people strong, are good, solid gamers in my opinion. And nice guys on top of that. What is the reason for this curse?

The only way I see to beat it is to start at a higher level. My next campaign will be 11th level. How's that curse!? Eat it!