Just for reference, for people not familiar with this issue, it has been discussed in:
Streets 2008 stopping after 5 to 6 weeks
* Yes, at least one person working for Microsoft stated at one time something to the effect that the cause of the problem was not yet known;
* I doubt Microsoft would give up on something like this, though.
My speculation is (and this is purely only a speculation), the issue may be related to the newly introduced activation scheme. Earlier Streets and Trips versions didn't suffer this issue. I've seen issues created in other products when they first introduced activation. But this is all just my guess. Let's see if any info comes our way.