FrozenBrain

It's not. The bug is reproducable on Vanilla servers as well.

This has been marked as fixed for a few days already so this bug will be gone in 1.4.4.

This is a problem with item frames (possible combined with maps in them). Destroy all of them to fix it.

https://bukkit.atlassian.net/browse/BUKKIT-2808?focusedCommentId=20400&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-20400