KEEP GETTING WEB PAGE ASKING TO PURCHASE THE PRODUCT AFTER PURCHASING IT.

I  downloaded the trial version of adobe Photoshop elements 10 about 30 days ago.  After the trail period was over, I purchased the product.  But now whenever I want to use the program to edit a picture, by either:

clicking directly on the picture and choosing adobe photoshop elements under the option to "open with"

OR 

after opening the adobe photoshop program, clicking on "organize" and then clicking on "edit with photoshop 10",

I get the window that says my trial period has come to an end. It then gives the option to "buy" the product, which I already did or enter the serial number.  So when after I type the serial number in, and I check to be sure that it's typed correctly, I get an error message that says the serial number is invalid.

SO WHY IS THIS HAPPENING?