Priority based levelling for split tasks having actuals

Hi,

I have seen below behaviour in 2007:
- A task A got split as there were some actuals before the start date followed by a work done on a different task
-Later there was a changing in project priorities with other project tasks getting higher priorities
- To make sure that half worked task A gets finished before any other task I set its priority to 1000
-Still pending part (after the split) of task A is prioritised after all the tasks having priority less to it! (I use Priority/Standard levelling; no splits allowed)

Why is that? To get around I had to delete actuals for Task A and then re-level.

thanks