AFAIK you will need a converter to go VGA > RGB
The reason I think this is because I've got an RGB>VGA converter to connect my TiVo to plasma and if I need a converter to go that way I can only assume I would need one to go back the other.
I got my converter from
www.js-technology.com and it might be worth you contacting him to see if his converter will work in reverse, but I doubt it as the pins used on the scart (and possibly the VGA) would be different.
Mark.