Create any database on a Domino Server 6.x+.
Create a document in the database and attach a document (eg an Office-Document or simply a Text-File).

Launch a Notes 7.x Client with a dedicated User with Editor rights (let's say User2).
Open the database and simply edit the document, so that it is soft-locked. It's not necessary to edit the attachment, just the document.
Launch a second Notes 7.x Client with a User1 (must be a different to User2).
Open the database and open the document.

Now try the following steps:

• Try to edit the document as User1. This will result an a prompt box, telling you that the document is locked by User2. Well, that's ok.
• Right Click the attachment and choose open. This will open the attachment with the associated app. Well, that's still ok.
• Double Click the attachment and choose open. This will open the attachment with the associated app. Well, that's still ok, too.
• Right Click the attachment and choose edit. This will tell you, that the document is locked by User2, followed by a second prompt box with some scrambled crap. Well, nasty, but you may live with that.
  
• Double Click the attachment and choose edit. This will tell you, that the document is locked by User2, followed by a second box, which is a nsd, and your client crashed. Well, that's not nasty, that'a a bug and you do not want to live with that.