An upload to flickr has failed, in itself a problem, and apparantly it'll take a while to fix it:
"""Flickr: failed due to 50:96: Invalid signature. Will be re-tried at 2011-12-19 00:25:26.0."""
We retry items that encounter errors up to five times over a day or so before giving up, in this case we've given up but we haven't yet added a message to explain this to you (thus the next retry is just displayed a long time in the future).
There seem to be a few items with this error in the system (which we pro-actively monitor so as to try and resolve such issues before you might spot them, and I apologise that we did not in this case!). We'll try and get it fixed ASAP as it is an issue from our end. Once items are failed permanently (for whatever reason) we do not retry them again, therefore you will have to do so manually.
BTW your issue with character encoding is still open, we haven't forgotten.