I have a similar problem as in this thread.
I've tried all the solutions here and I don't have any conflicting scripts. (change file permissions to 777, edit the images.php file) This didn't change anything.
My nivo slider loads and images are link to the correct image path. However I don't see the images inside the nivo slider.
I get the following error that repeats each time the image switches.
GET http://us4test.com/us4interactive/wp-content/plugins/shortcodes-ultimate/lib/timthumb.php?src=http://us4test.com/us4interactive/wp-content/uploads/2012/05/us4logo1.png&w=500&h=300&zc=1&q=100 400 (Bad Request)