By the sound of it, it's not releasing the override keybindings for B(lue), R(ed), Y(ellow), G(reen) and C(lear). Merely closing the frame should, and does, as far as I can tell, return control to the usual keybindings for the affected keys. The only thing that comes to mind is that you may be closing the frame in combat, when addons are unable to change your keybindings (and hence Ogri'Lazy is unable to release the keys when it tries to do so) -- try closing the frame while out of combat and see if the issue persists.

I'll have another look at this and update the version uploaded here later in the week.
Update: 1.0.5 should solve both issues reported here - Ogri'Lazy should appear automatically in non-English clients, and it'll release the hotkeys associated with it after you exit combat if you close it in combat.

That wouldn't work here - Blizzards own key bindings UI is based around keybindings that persist - rather than appear when you start interacting with something and disappear when you're done. Binding/Unbinding default keybinds would create an even bigger mess, which could even be saved to your local settings if you're disconnected from the server while the keys are remapped.
Asking the user to remap those manually every time they wish to use the addon seems like overkill.

You can use the fifth icon in the bottom row to clear the current sequence (English hotkey: C). There is no "backspace" at the moment, although that may actually be a worthwhile feature