OK, so obviously SOME code is running, but that doesn't mean that the method that opens the frame will ever be called. Without looking at the code, it's impossible to tell what's wrong here. But it's most likely a problem with your code, not with JBuilder. The fact that it doesn't work in Netbeans seconds this.
Maybe you can post the code if it's not too large!?
About the textures: Please check their width again. jPCT checks for the width in a switch-case statement. Supported widths are 8,16,32,64,128,256,512,1024,2048,4192. Everything else will be scaled down (or up) to 256. The same is true for the height.