From Feb 1-14 Briefing Packet:

Due to United's current financial situation, Cabin Defense Security Training - Phase II (DS2), scheduled to resume in April, has been delayed until further notice. As a result, current preference month awards are no longer valid. Flight attendants holding a preference month for this program should plan to re-bid for a preference month when the program resumes and the new class schedule is communicated.

We continue to review the financial feasibility of starting this successful program on a monthly basis with the hope that we will be able to do so as soon as possible.

Well, there you go.  Perhaps it's time to re-publish the defense class information we had posted here several months ago!