Certain wiki markup is causing database errors when you use Confluence with a DB2 9.7 database. Add the following markup to a new page:

!&&&&&!

Now go to the preview tab and you will see an error like:

Hibernate operation: Could not execute query; SQL []; DB2 SQL Error: SQLCODE=-302, SQLSTATE=22001, SQLERRMC=null, DRIVER=3.57.82; nested exception is com.ibm.db2.jcc.am.co: DB2 SQL Error: SQLCODE=-302, SQLSTATE=22001, SQLERRMC=null, DRIVER=3.57.82

If you end up saving the page, you will be greeted with an error page and full stack trace. At this point the only way back to a working page is to hack the URL and go to <your-confluence-url>/pages/editpage.action?pageId=### where ### is the pageID of the broken page.

In any case, this has something to do with the database transaction and the presence of five ampersands directly between the two exclamation points without any breaks or spaces between them.

!     !

also causes the error.

For what it's worth, this seems to be a bug with Hibernate:
http://opensource.atlassian.com/projects/hibernate/browse/HB-1567