Help! Need help with .png files for ObjectDock. Please help me.

I was trying to make an ObjectDock icon for my first submission to Wincustomize - a runescape icon. When I made the file and then converted it to a png image, it all worked perfectly. I put it in the right spot (C:/ProgramFiles/ObjectDesktop/ObjectDock/mytheme/) and then opened the runescape program. I right-clicked on it and selected "Set image for this Program." I selected my icon and pressed ok, but it gave me an error prompt! It said "
Runtime Error!

Program: C:\...\ObjectDock.exe

This Application has requested the Runtime to terminate it in a usual way. Please contact the application's support team for more information."
Please tell me what to do.