I have the same issue when if I exit from the Analysis board in the app and try to complete the tactic. Is that what you are seeing?
Below is the topic I posted about it in the Android app group/forum:
http://www.chess.com/groups/forumview/minor-tactics-trainer-bug
I get the same thing on Android 2.3.7 and 3.2.1.
I was doing TT with the chess android app on my galaxy tab.
it told me that I have reached my daily limit and I should sign of for a subscription. What happened since I already have the "best" subscription.