If this was a recent purchase for which you have a receipt, return it to the store immediately while you still can. If it is beyond the store's return policy, but purchased less than one year ago (most times you will still need a receipt), call Black and Decker to get in-warranty service/replacement.
In fact, call Black and Decker anyways - if the BL5000 was manufactured between Dec.2003 and Jan.2005 (highly possible if it was marked on clearance), the blade assemblies were recalled. here is the recall notice:
If it is out of warranty, let the blender cool for an hour. Then remove the blender jar, plug in the base, and see if it will spin with nothing attached to it. See if it smokes if left on for 1 full minute - don't let it run longer than one minute.
If it doesn't smoke, let it cool for an additional 20 minutes. Then remove and then reassemble the blade assembly, gasket, etc., collar, jar, etc. Try blending. If it smokes while blending, order a new blade assembly and gasket (usually they come packaged together - around $20 or so). Once the new blade assembly/gasket arrives, try blending again. If it doesn't smoke, you're probably good to go. If it does smoke, you have a more serious issue.
All of this is going to take time and money if it is out-of-warranty. If you have deemed that the blender is worth more than $50 for a new one, let me know.