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. There is also a step posted for server "troubleshooting". If your problem is occurring with a server that is hosted on your computer, please complete all steps, as well as the server "troubleshooting".
If you continue to have trouble, 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