Security configuration disallowed the connection

Yesterday morning, I started getting this message when trying to deploy
to my HTC TP2 (T-Mobile).

I think I understand the error - I've had to deploy development certs to
a smartphone device in the past. But there are three things about this
error message that strike me as very strange:

1. This is happening on a WM Professional device with regular one-tier
security.
2. I had been debugging on this device previously - in fact I was
deploying to the device earlier that day and got the expected prompts on
the screen asking me if I wanted to allow it.
3. Finally, the other very interesting thing is that a coworker had the
same problem just start yesterday on a different TP2 (AT&T demo).

What would cause two different phones (same model, different carriers)
to suddenly start acting like two-tier security devices?

Or do I just not understand the problem?

Thanks for any insight into this problem,
Shane