On HEAD org.jasig.portal.layout.dlm.RDBMDistributedLayoutStore in the methods:

getFragmentLayoutCopies()
initializeFragmentCleaner()
getUserLayout() getStructureStylesheetUserPreferences()
getThemeStylesheetUserPreferences()

there is a broken double checked locking idiom:

if ( ! initialized )
        {
            synchronized( initializationLock )
            {
                if ( ! initialized )
                {
                    initializationLock.wait();
                }
            }
        }

For more info about double checked locking see:
http://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html

Also, in getThemeStylesheetUserPreferences() the first if test seems to be missing a "!" and the block would only be entered if initalized was already true.
        if ( initialized )
        {
            synchronized( initializationLock )
            {
                if ( ! initialized )
                {
                    initializationLock.wait();
                }
            }
        }