Impossible to edit lesson's text

I tried to modify some texts in lessons created by myself. It was possible to edit Title, Description, Category, etc. But it does not allow to edit the Text field.
I tried to edit a typo in IE, FF, Opera, Chrome on WinXP and Win7. It’s easy for the Description field but it’s absolutely impossible for the Text one. Why?

If you are a free user, only 5 private imports OR changes are allowed.

It explains. Thank you.

Hello! I imported one private lesson the other day. Then I tried to do that again, but I could not, because there was a message that I was not allowed to add the new private imports due to my free account, even though, I imported only one lesson. Could you explain me why it is?

Imported lessons whether you archive or delete them still count against your limit. Also note that this limit applies across all languages in your account.

Thank you mark. I seem to figure out why it occurred.