can u try at another location? maybe u have some issues with your network environment?
did it work before?
can u send me the log file?
you can find the log file in the data directory under those locations:
Mac OSX: /Users/username/Library/Application Support/Bitsquare
Windows 7,8: C:\Documents and Settings\username\AppData\Roaming\Bitsquare
Windows XP: C:\Documents and Settings\username\Application Data\Bitsquare
if u dont have bitcoins in your wallet and no offers/trades/disputes open you can remove the current data directory and start over again so a new one will be created (backup first the old one). maybe that helps?