Strange dates and text "NaN days ahead" Rated 5 out of 5 stars

I'm seeing dates in the CP 1.2.3 dialog like this:

Issued On: 203/12/2010 0:00:00 AM (35 days ago)
Expires On: 203/25/2012 23:59:59 PM (NaN days ahead)

Is this due to a bug? If not, how do I interpret that date which is supposed to be 35 days ago?

This review is for a previous version of the add-on (1.3.1). 

It's a bug

... that I have fixed a month ago, but some new problems keep creeping up making the new versions (1.2.4, 1.3, 1.3.1) not 100% stable. I stepped back and uploaded a 1.2.5 which only fixes the bug in 1.2.3. It should appear soon or you can install it manually from https://addons.mozilla.org/en-US/firefox/addons/versions/6415 – At the same time I have 1.3.5 ready which should also fix the new bugs, but I can't upload it at the same time, so it may take a while until you get the "current" version of CP.