What roms are you trying to run (please be specific)?
I have found that the problem you are describing could be one of several reasons:
Reason 1 = If you dont have the Nintendo 64 emulator installed in default place or if its not installed at all, it will just look like a blank- black screen when you hit a v64 or n64 rom file.
Reason 2 = If you are trying to open a file that is damaged or incorrect to its file extension.
Reason 3 = If you have installed Mobile Impact to its default directory then changed the directory name or changed the emulator directories for any reason it will result in the program not being able to locate the emulator.
The main thing that you should look for is a missing emulator program file.
In the C:\Program Files\Mobile Impact you should have a GBA, NES, Sega, and Snes Directories where the emulator executable are located. You should also have in the C:\Program Files directory the \Project64 1.6 directory. any variation from this will have the effect you are describing. Hope this sheds some light on it.