Forest Temple Problem

[Hyrule Guardian]

I was playing The Legend of Zelda: Ocarina of Time. It was beautiful until this day. When I try to open the locked door in Forest temple (I have the key) the ROM crashes with an message, "Fatal Error: Stopping emulation." What does this mean? Is there any solution for this?

[Hyrule Guardian]

I'm the one who is dumb. I was trying to use another key. I headed to the north door, killed 2 monsters and got the key.