Account is blocked by dunning run

Hi,

after i have run dunning for customers and if i look into log i see that for some customers dunning didn't run.

Account D 0000010900 is blocked by dunning run 20080820 82008.

There is any transaction where i can block/unbloc customers for dunning? From where came that blocking?

Any idea/hint/clue would be apreciated.

Thank you.