It would be very useful if the submit view automatically selected the task for which the user did the last submit in current contest. The motivation for this is:
1. If the user is going to submit a solution to the new task, he/she is going to pay attention to selecting the proper problem.
2. If the user is going to resubmit (possibly n-th time) the solution, he/she is less likely to pay attention to selecting the problem and hence is much more likely to submit the solution to the wrong task.
Now the scenario in 2 is pretty frustrating for the user, because I can imagine some ranking views which take into account the time of the first submission/last submission/number of submissions of a task. Mistakingly submitting code with no option to revert this and therefore - losing points by a very stupid mistake is a situation of which the odds should be minimized by the system as much as possible.