NAV 12 subscription

I'm running Mac OSX 10.7.3 on my desktop. I purchased Nav 12 on Nov. 30th 2011 and am now running NAV 12.2

Appx. a month and a half ago it told my my "trial" was running out an subscription key was needed.  I found the e-mail from when I bought the NAV and put the key in and no problem... until yesterday when it did it again.  I put the key in again and it looks like it's working fine.

My question is: why is it doing this?  It seems to be working fine other than this and this isn't a big problem, just a pain to deal with.

 

Any suggestions?