Welcome. We need a log, either an error log or preferably a console log. To get the console to reappear ensure that 'Show Console?' and 'Reopen launcher after exiting minecraft?' is checked in the Options tab. Close and reopen the launcher and try to run one of the 1.6.4 packs again. If it reopens press the 'Paste my log to pastebin.com' button. This will add a link at the bottom of the console. That is where your log is saved, post that link here. If it does not reopen or copy please copy it over manually or find the error log in the minecraft folder of the 1.6.4 pack and copy that to pastebin.com manually and provide us the link that it gives.