As John said, stick to one brand of Card throughout your configurations.
Thats asking for trouble.
I was looking at the 4 and 8GB versions of the following cards:
Makes no real difference when using Vegas.
Steve Rhoden (Cow Leader)
Film Maker & VFX Artist.
Owner of Filmex Creative Media.
Samples of my Work and Company can be seen here:
https://www.facebook.com/FilmexCreativeMedia