Please change the rewrite on download.m.o to point at 'product=firefox-3.6.4-euballot' instead of 'product=firefox-3.6.3-euballot'. Previous bugs 556953, 554261. It's possible this has changed as a result of bug 557271 comment #3 - I can't find that bug if it was filed.
Sorry that's a bit ambiguous. We'll be redirecting download urls from product=firefox-latest-euballot -> product=firefox-3.6.3-euballot and that should change to product=firefox-latest-euballot -> product=firefox-3.6.4-euballot
Verified, thanks Shyam.
[Note for 3.6.6 - we could combine the changes in bug 573905 with this]