The interactive tools are not working, but this script will clear a stubborn log file that won't release.

Link here

http://stackoverflow.com/questions/56628/how-do-you-clear-the-sql-server-transaction-log

Assumption: You are in simple mode

USE TheDatabase;
GO

CHECKPOINT;
GO

CHECKPOINT; -- run twice to ensure file wrap-around
GO

DBCC SHRINKFILE(TheDatabase_Logical_Name, 5); -- unit is set in MBs
GO;