Can't unshared or delited shared documents

Can't unshared or delited shared documents

Hi!

my VO v.3220 on winXP SP2

I can't to unshared previously downloaded and shared text document - (because in "Shared To User(s)/Groups" windows I have nothing to see);
I can't delete (Access denied. The item's is shared.);
I can't edit or view previously downloaded text document (when I click on icon "edit" in left corner of IE appears yellow triangle "Error on page").

How I can fix this bug?