Thanks for testing my instruction theory but I believe you probably had it working all along or java wasn't letting you test your actions.
The Forge_1.7.2 (mcp) uses some jre-1.7 specific code that is updated in or after jre-1.8_11 through _20
So while using Forge 1.7.2, We should use jre 1.7 update 67 to 75.,
( MC 1.7.10 uses the updated code.
so 1.7.2 users should not update past 1.8_11 just to be safe ?)
This looks like a java 8 error ( After Java8_11, some Iterator stuff gets weird )
Install Java 7 update 75 for 64bit windows (below) along side your current java install and then give it a whirl.
Simple method ^
Or remove Java8 first then install Java 7 update 75 -x64
I also recommend to disable the Java update service.
get the windows x64
You do not need the 7u76 version which is a PSU release.
Only the 7u75 is what you need and is ok along side Java 8 but I would get rid of Java8 and only use Java7 update 75 to 78 to have a stable java setup for older versions (for now anyway)
Soon java8 will be all fixed up and ready for the billions of devices and java7 will be a memory.
This should fix your issue if it's because of java 8.
During installation of any program, Always read the fine print and un-select any 3rd party offers.