Yeah I got some problems with java too.
I have Java7 u3 installed, and whenever I start the Technic launcher (the one the downloader has downloaded).
It starts fine, but whenever it wants to download all the files, it just stops, freezes, and after about 1 minute it says: failed to download.
This happens too with normal Minecraft (Minecraft just crashes completely), Java 7 just cannot download it completely.
Anyways, If i try to install Java 6, and launch it with java 6 (C:\Program Files\Java\jre6\bin\javaw.exe), it start up Java 7! C:\Program Files\Java\jre7\bin\javaw.exe.
So, after de-installing java 7, it works fine (it uses java 6). it just downloads everything without problems. after the download of all files, i re-installed Java 7 again, and played it with java 7.
So i thought: This shouldn't be this hard! so i made some scripts, and finally i came up to this:
'Start w Java6.cmd':
"C:\Program Files\Java\jre6\bin\java.exe" -Xmx2G -Xms512M -jar technic-launcher.jar
and:
'Start w Java7.cmd':
"C:\Program Files\Java\jre7\bin\java.exe" -Xmx2G -Xms512M -jar technic-launcher.jar
I placed these files in the .techniclauncher folder. now whenever i wanna download the Technic files again, i choose the 'Start w Java6.cmd', and whenever I just wanna play it without downloading, i choose 'Start w Java7.cmd'
PS: All versions of Java is 64 bit
I hope this will help for some of you.