confluence suddenly unusable -- java error

System Error
A system error has occurred — our apologies!
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The SystemInformationService could not be retrieved from the container. Therefore very limited information is available in this error report.
The SystemInformationService could not be retrieved due to the following error: java.lang.NullPointerException
Cause
com.atlassian.util.concurrent.LazyReference$InitializationException: java.lang.NullPointerException
at com.atlassian.util.concurrent.LazyReference.getInterruptibly(LazyReference.java:152)
caused by: java.lang.NullPointerException
at com.atlassian.spring.container.ContainerManager.getComponent(ContainerManager.java:33)

If you get this error message, permission error may cause this error.
To solve it,
1. Go to your confluence home directory
2. list all items with ls -al

testwww1:/usr/local/confluence-data# ls -al

total 152

drwx--S---  19 confluence confluence  4096 2012-08-20 10:27

(...)

drwxr-sr-x   2 root       confluence  4096 2012-07-10 15:41 plugins-cache




3. Then, (Our) Confluence is running with confluence user, so permissions were wrong (without writing for group). When I changed owner with:

chown -R confluence:confluence confluence chown -R confluence:confluence confluence-data

 and restarted Confluence with

/etc/init.d/confluence restart

 it raised up and is working. Hope you will find it useful :)