-1,091,273 BOINC points on 8 Oct 2012. Why does this happen and how do I fix it?

... shortly after updating my BOINCstats email. Could that have caused the problem?

From the FAQ:

Why do I lose credit in BOINC combined stats?

When you attach to a new project, or reattach to a projects that restarts after a 'break' your CPID for a project can change. It takes a while for all projects to line up again. During this time, you may lose some credit in the combined stats, and sometimes all credit will go to a new account with a new CPID.

That seems to be what happened. GPUgrid shows a different CPID from the one on BOINCstats, and that CPID shows all my BOINC stats, so I just punched "renew CPID" in spite of the warnings.

• Only renew the CPID when your CPID no longer links to your stats correctly. To prevent waste of bandwidth for both BOINCstats and the projects, there is a limit on the use of this option over a certain period of time.
  
• "Renew CPID" only updates your BAM! CPID. It does NOT change any CPID at any project, it will NOT affect your stats, it will NOT fix a split CPID! Only the link between BAM! to the stats may be affected when the new CPID is different than the current one.
  

Oh well, BOINCstats is still pretty cool, for the price. Thanks, Willy!