I've been getting this exact problem for a while now when I try to upload photos to any album. Currently, I just keep re-publishing and eventually the pictures get through, but I get some duplicates. Would love to get a solution for this! It's a huge pain!
I am also receiving the same error when trying to publish pictures to Facebook (note: previously - several months ago - I was able to publish to Facebook just fine *without* receiving this error. Also, I don't have issues with other Lightroom 4.2 publishing plugins):
- Lightroom 4.2
- Mac OSX 10.7.5
(agree with both posters that this is a *huge* pain)