ERROR XmlConfigurator error with Nant on mono 2.8

I tested with simple nant (0.90) on Mac OS X 10.6.4, but I got the following error message. Even with the error message, I could run nant to get the binary successfully.

What might be wrong?

log4net:ERROR XmlConfigurator: Failed to initialize configuration file watcher 开发者_运维技巧for file [/Library/Frameworks/Mono.framework/Versions/2.8/share/NAnt/bin/NAnt.exe.config]
System.DllNotFoundException: libc.dylib
  at (wrapper managed-to-native) System.IO.KeventWatcher:kqueue ()
  at System.IO.KeventWatcher.GetInstance (IFileWatcher& watcher) [0x00000] in :0 
  at System.IO.FileSystemWatcher.InitWatcher () [0x00000] in :0 
  at System.IO.FileSystemWatcher..ctor () [0x00000] in :0 
  at (wrapper remoting-invoke-with-check) System.IO.FileSystemWatcher:.ctor ()
  at log4net.Config.XmlConfigurator+ConfigureAndWatchHandler..ctor (ILoggerRepository repository, System.IO.FileInfo configFile) [0x00000] in :0 
  at log4net.Config.XmlConfigurator+ConfigureAndWatchHandler.StartWatching (ILoggerRepository repository, System.IO.FileInfo configFile) [0x00000] in :0 
  at log4net.Config.XmlConfigurator.ConfigureAndWatch (ILoggerRepository repository, System.IO.FileInfo configFile) [0x00000] in :0 

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export DYLD_FALLBACK_LIBRARY_PATH="/usr/lib/:$DYLD_FALLBACK_LIBRARY_PATH" should have been in bash file.