I'm not sure how wide-spread this is yet. But it seems to be a systemic problem due to the way that wikistats csv files are processed into Limn files. One example:

http://reportcard.wmflabs.org/graphs/new_editors

If you download the CSV, which is accurate, you'll see that the "Japanese" column is actually being graphed as the "German" column. This has been happening since the beginning of this version of the reportcard, my estimate is sometime around June 2012.

Version: unspecified
Severity: critical