[ERROR]: FileSystemPreferences syncWorld ?

I just upgraded to 2.1 and during the nightly build on a Ubuntu Linux
box I see the error listed below
I am not sure what to do with it? Is it simple an error, or can I
ignore it?

I also notice the following old closed issue that describes something
similar:
http://code.google.com/p/google-web-toolkit/issues/detail?id=2092

What to do with this error? How do I solve this?

----
INFO] [compiler:compile {execution: default-compile}]
[INFO] Nothing to compile - all classes are up to date
[INFO] [gwt:compile {execution: default}]
[INFO] Compiling module com.bv.gwt.login.LoginProd
[INFO] Compiling 5 permutations
[INFO] Compiling permutation 1...
[INFO] Process output
[INFO] Compiling
[INFO] Compiling permutation 0...
[INFO] Compiling permutation 2...
[ERROR] Dec 27, 2010 2:26:51 AM java.util.prefs.FileSystemPreferences
syncWorld
[ERROR] WARNING: Couldn't flush user prefs:
java.util.prefs.BackingStoreException: Couldn't get file lock.
[INFO] Compiling permutation 3...
[INFO] Compiling
[INFO] Compiling permutation 4...
[INFO] Compile of permutations succeeded
[INFO] Linking into /home/develop/gwt/work/prod/login
[INFO] Link succeeded
[INFO] Compilation succeeded -- 88.432s
[INFO] [antrun:run {execution: default}]
[INFO] Executing tasks
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