I am having similar issues.
Been trying to help a friend with a crashing client. This might not be the cause but FTB launches jre6 as the preferred JRE.
[18:41:55] [INFO] JGoogleAnalyticsTracker$2.run:483: AnalyticsBackgroundThread started
[18:41:56] [INFO] LaunchFrame.main:185: FTBLaunch starting up (version 1.3.5)
[18:41:56] [INFO] LaunchFrame.main:186: Java version: 1.6.0_14
[18:41:56] [INFO] LaunchFrame.main:187: Java vendor: Sun Microsystems Inc.
[18:41:56] [INFO] LaunchFrame.main:188: Java home: C:\Program Files\Java\jre6
[18:41:56] [INFO] LaunchFrame.main:189: Java specification: Java Virtual Machine Specification version: 1.0 by Sun Microsystems Inc.
[18:41:56] [INFO] LaunchFrame.main:191: Java vm: Java HotSpot(TM) 64-Bit Server VM version: 14.0-b16 by Sun Microsystems Inc.
[18:41:56] [INFO] LaunchFrame.main:192: OS: amd64 Windows 7 6.1
[18:41:56] [INFO] LaunchFrame.main:193: Launcher Install Dir: C:\Users\<Username>\Downloads
[18:41:59] [INFO] LaunchFrame.main:194: System memory: 2612M free, 4092M total
[18:42:14] [INFO] LocaleUpdater.run:67: [i18n] Checking for updates ...
[18:42:14] [INFO] I18N.setLocale:127: [i18n] enUS English language file loaded!
[18:42:18] [INFO] LocaleUpdater.run:80: [i18n] remoteVer = 10
[18:42:20] [INFO] LocaleUpdater.run:93: [i18n] localVer = 10
[18:42:20] [INFO] LocaleUpdater.run:98: [i18n] Files are up to date
[18:42:21] [INFO] I18N.addFiles:104: [i18n] Fallback enUS loaded
[18:42:43] [INFO] JavaFinder.parseWinJavaVersion:103: The FTB Launcher has found the following Java versions installed:
[18:42:43] [INFO] JavaFinder.parseWinJavaVersion:105: Java Version: 1.7.0_51 sorted as: 1.7.0_51 32 Bit Java at : C:\Program Files (x86)\Java\jre7\bin\java.exe
[18:42:43] [INFO] JavaFinder.parseWinJavaVersion:105: Java Version: 1.6.0_14 sorted as: 1.6.0_14 64 Bit Java at : C:\Program Files\Java\jre6\bin\java.exe
[18:42:43] [INFO] JavaFinder.parseWinJavaVersion:105: Java Version: 1.6.0_14 sorted as: 1.6.0_14 64 Bit Java at : C:\Windows\system32\java.exe
[18:42:43] [INFO] JavaFinder.parseWinJavaVersion:105: Java Version: 1.7.0_51 sorted as: 1.7.0_51 32 Bit Java at : C:\Windows\SysWOW64\java.exe
[18:42:43] [INFO] JavaFinder.parseWinJavaVersion:124: Preferred: Java Version: 1.6.0_14 sorted as: 1.6.0_14 64 Bit Java at : C:\Program Files\Java\jre6\bin\java.exe
...
The class net.ftb.util.winreg.JavaFinder selects a preferred java installment of all available ones, but this is done after itself launches in a 1.6 JRE.
It is a windows machine.
JAVA_HOME env is set to C:\Program Files (x86)\Java\jre7\bin\java.exe and using 'java -version' in cmd gives 1.7 as well. The system preferres 1.7 but for some reason the launcher and net.ftb.util.winreg.JavaFinder thinks otherwise.
Help appreciated.
