I'm having the same problem as you. As for the contents of the launch.bat file, is this it?
java -Xmx3G -Xms2G -jar Tekkit.jar nogui
pause
That's what it says in the notepad, and I've tried changing the 3G and 2G to 1G and 1G, and even 1024M and the same, but it still doesn't work. Can you think of anything?