Problem in the planning worksheet (NAV 5.0)

Hi all,
I have a problem with the planning worksheet in Microsoft Dynamics NAV 5.0 SP1.
When I click on Functions → Calculate Regenerative Plan (in the Planning Worksheets) for an item (art-code-001 for example), if the stocks of this item (art-code-001) is 0 (ZERO) and there are no sales orders and there is a reorder point set in the stockkeeping unit (Fixed Reorder Qty is the reorder policy), NAV does NOT propose production for this item (art-code-001) and make no proposal to transfer in our transfer location code.
Putting a positive stock LESS THEN reorder point, the system works perfectly.
The system works properly even if the stock for the item art-code-001 is LESS THEN 0 (-3 for example).
The problem occurs when the stock is equal to ZERO (= 0).
Transfer Routes are correctly set.
This is a crazy behavior, maybe there is a bug in the C/AL code in some code unit.
I hope this is the right forum to post.
Thanks in advance for your reply.