Please follow these steps exactly:
http://desk.feed-the-beast.com/index.php?/Knowledgebase/Article/View/9/0/basic-troubleshooting
This is to rule out any issues with your setup. Please also read the extra info at the bottom of the guide, and apply all applicable suggestions.
Please post your complete client-side (launcher) console log in debug-mode to pastebin.com and link your paste URL here.
To find your logs and prevent them from expiring:
http://desk.feed-the-beast.com/inde...29/1/what-log-do-you-need-where-can-i-find-it