The latest release of Java, version 8 update 25, which was released on October 14th, may stop your modded Minecraft 1.6.4 profiles from running.
We’ve had a couple of reports from users this week who experienced their Minecraft 1.6.4 modded profiles just simply not opening, after clicking Play, it would start to load then profile then just close down. The installed version of Forge was 1.6.4-126.96.36.1995.
Simply uninstalling Java version 8 via the Control Panel, then installing Java version 7 from this page: https://www.java.com/en/download/manual_java7.jsp immediately fixed the problem.
We normally encourage people to stick with the latest releases of software, especially important ones like Java. But if you love some of the mods that haven’t been updated past Minecraft 1.6.4, then don’t worry, the latest Java 7 is still secure. Besides, who doesn’t like the feel of a tropical beach in Minecraft with the Tropicraft mod!
Feel free to comment below if you have any questions.