again "normal"...
This is the same beheviour as if you block/unblock an entire group rapidly or multiple times (you will notice the result/beheviour much better). You need to give Messenger and the servers some time to process the block/unblock, otherwise they will be confussed. (It only takes 1 packet to be lost/out of sync/whatever and the indicator will not show the correct status)
However, this could be prevented I imagine, but this is far from top priority I asume (as blocking/unblocking isn't meant to do multiple times after each other (before the previous status is processed))...
If you wish you could report the "bug" to MSN:
http://messenger.msn.com/help/contactus.aspx
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