When a page contains a link which contains the string '[::]', then migration can fail with the following error in the logs. Please also see the attached screens shot which shows the migration failing in the UI.

2013-05-14 11:24:02,176 FATAL [main] [atlassian.config.lifecycle.LifecycleManager] panicAndShutdown Unable to start up Confluence. Fatal error during startup sequence: confluence.lifecycle.core:pluginframeworkdependentupgrades (Run all the upgrades that require the plugin framework to be available) - com.atlassian.confluence.content.render.xhtml.migration.exceptions.MigrationException: java.util.concurrent.ExecutionException: java.lang.ArrayIndexOutOfBoundsException: 1
com.atlassian.confluence.content.render.xhtml.migration.exceptions.MigrationException: java.util.concurrent.ExecutionException: java.lang.ArrayIndexOutOfBoundsException: 1

The reason appears to be that the link interprets '[::]' as an array for the link. For example, the text could be 'http://www.atlassian.com/[::]'

Steps to Reproduce

1. Install a version of Confluence older then 4 (say 3.5.17)
2. Create a new page and paste 'http://www.atlassian.com/[::]' to be the body of said page
3. Upgrade to any version of Confluence greater than 4
4. Upon startup, we will receive an error stating that the upgrade has failed to an array index error.

Workaround
See Wiki Markup Migration Fails with Array Out of Bounds Exception