No problem with the poor English
You aren't overloading or overriding the property are you? ViewSecurityKey is actually implemented way down in the SF BaseForm, with is sub-classed by the SF StandardForm, which your master form is using....so I don't know why it wouldn't work for one more level. So it probably likely that you are doing something on the accounts form that is messing things up.
I'd try a couple of things to narrow down the problem. First, check our security key and also the user your testing with, make sure everything is setup correctly. Next, if you have another form that is inherited from master, attempt to do the same security on it (temporarily, just for testing). If that also does not work, I'd create a new form with no code, just the security key, inherit from master. If that does not work, create a sample app, see what happens.
Also, what exactly is it doing? Always opening? Throwing an exception?