Looks like about the same set up I have on my boards. I looked over at the InVision site forum and one of the messages there mentioned setting the permissions of the uploads directory to 777 in order to allow writing to it so that is probably the problem. I think mine defaulted to 755 when I installed and I couldn't upload to it until I changed it.
In any event, I enjoy the board and have enjoyed playing with getting my site transferred over and playing with some new things. It is bitterly cold here in Greenville, at least for us. I teach math at a High School here and we had classes cancelled last Friday, yesterday, and today so I've had plenty of time to play. I set up some online quizzes for my students and played with PhpNuke to see how it works.
Great service...keep up the good work!