I am using the latest CCleaner 5.11.5408 and have found that it does not clean the "Media Cache" folder of the latest Opera browser (v33.0). The "Cache" folder is cleaned but it misses the "Media Cache" folder.
In the meantime you can manually add it into CCleaner so that it gets cleaned using an Include, see how here:
http://www.piriform.com/docs/ccleaner/using-ccleaner/including-files-and-folders-for-cleaning