At the moment, the main BOINCstats page shows Total Credit for BOINC combined and Rosetta as exactly "100,000,000,000,000" and the last day scores are "99,992,883,033,081" and "99,999,875,401,372" respectively.

Accepting that the root cause is something to do with Rosetta, the problem seems to have unearthed a couple of other bugs:

The Total Credit value seems to have maxed out at 100 trillion (the numbers don't add up at the moment). And the last day figure for BOINC combined is less than the last day figure for Rosetta. It will probably take a while before the real scores hit this level though.

Did something barf during the last Rosetta stats run perhaps?

Problem solved. Was an error in the XML export of Rosetta.