Pushing the button just causes the Display to turn on, the code that is displayed is an encription of the Time of Day (likely rounded to 30 sec) and the Fob serial number.

Quote Originally Posted by aboron View Post
(there is probably also some tracking server side for the previous and next valid numbers to account for the timebase drift that likely happens on the keychain unit, since it is bound to be significant and would vary with temperature and such)
I suspect it is the Time of Day tracking on the Server side that is issue. When the servers decript the code they get the Time of Day on your Fob. On the Servers they are keeping up with the drift from real time for each Fob on each account in their system, other wise your FOB would stop working when the internal clock drifted too far off real time.

I am thinking that when you log into one Battle.NET account 5 times, it does not like five different FOB time of Day updates in a row with the same TOD, and rejects them. The drift calculation may not like Zero time difference from the last log on. Where as when the accounts were seperate they got a single FOB time of Day Update on each account accross your Five acounts, and then they where keeping up a seperate Drift calculation on each account.