Unfortunately this is a known issue on our end (seems to be specific to BO) which we are working on correcting. If you attempt to log in a second time it seems it goes through. We appologize for the inconvenience and mixed message.
I always believed that "feature" of the PSN to be backwards.
In cases of legitimate duplicate IDs (for example, having two PS3s and accidentally logging into the second PS3 with the ID already on the first), the PSN should stop the second log-in attempt, rather than unceremoniously log off the first ID without a warning.
We have lost Warhawk hosting sessions (abeit only once since it was such a big deal) with a great game of 24 people due to accidentally logging into the second PS3 with the ID that was hosting the game on the first PS3.