When saving a page which contains a emoticon inserted like this:
(?)
... i get a NoClassDefFoundError for com/atlassian/confluence/content/render/xhtml/storage/inline/StorageEmoticonMarshaller.
Inserting the emoticon using the insert more content menu works.
Couldn't find anything about a bug like this, so i assume it's a configuration issue. Maybe some plugin that needs to be actvated. I'm running on Confluence 5.5.2.