*Pow*

It looks like my cross-posting problems from the last few days were not restricted to my blogs alone; more than a few people have encountered the same issue, and Multiply is now having a look. So far I've noted at least one possible solution, to be found here. The excerpt below comes from Jen of Multiply support:

Thanks for bringing this to our attention... it's being looked at now. In the meantime, you can reset your Blogger cross-posting by following these steps:

1) Initiate an import from Blogger (Post --> Blog --> Import Blogs (Blogger))
2) At the login dialog, check the Enable cross-posting between Multiply and Blogger box. Click OK
3) Once you've logged in, exit the dialog so you don't re-import all your blogs again.

This will reset your cross-posting. We'll let you know when we've fixed this issue properly.

I've followed the above steps already, and I'll be testing it shortly. Once I'm sure that it works, I'll get back to our regular scheduled programming.