Virtual Combat Cards has been design trying to make it resistant to problem, so that you don't lose you combat. Eventually a bug might popup and may cause it to stop it's normal behavior. If this happens please report the bug, but don't panic there are ways to recover you combat.

The internal tracker is quite resistant to problems, and most of the times you should try the following before giving up:

1. Show the dead combatants (if you have hidden them); most of the problems with starting and ending rounds, is caused by a dead combatant lingering on the top o the sequence list.
2. Use the Undo command (Ctrl + Z) to undo the last command; you can normally undo the combat until the very beginning of the battle. If you can figure out what happened to lead to the bad behavior, this will help us fix it quickly; If you wish to redo use the redo command (Ctrl + Y).

If all fails, take a screen-shot of the combat sequence and the logs, and open a bug report.