Windows .exe Game does not launch -> ClassNotFoundException

[AyvenRedwing]

Operating System and bit type: Windows 7 (64 Bit)
Java version/update and bit type: 1.7.0_25 (64 Bit) & 1.7.0_17 (32 Bit)
Launcher version: 1.3.2
Console log, pastebin.com link: http://pastebin.com/BCAPq8Qr

I newly updated the Launcher to version 1.3.2 and wanted to test one of the new modpacks (no additional mods or texture packs installed.). After pressing the Launch-button, most button got grayed out, because the launcher was loading. Since nothing happened for 30 minutes after the modpack was downloaded, I attempted the standard trouble shooting and retried.
This time I checked the console and saw that it was throwing a ClassNotFoundException, as you can see in the pastebin.

The launcher always worked fine in previous versions.
Standard minecraft launcher is working fine as well.

 

[lavarthan]

Do you really need to run all those out-of date versions and any 32bit? Try uninstalling all Java, restart your computer. Then install only Java 7u45 64bit.

 

[AyvenRedwing]

Do you really need to run all those out-of date versions and any 32bit? Try uninstalling all Java, restart your computer. Then install only Java 7u45 64bit.

I wasn't aware of how old my Java version was. I changed it to the newest version and reinstalled FTB.
Sadly, the problem persists.

EDIT: After fiddling around with the launcher and the corrresponding folders for several minutes I somehow managed to fix the problem.
I sadly can't say what exactly the solution was, but it works now.