"can not download" is, unfortunately, not adequate information to understand your situation, which is of course required to provide useful assistance. Please tell us exactly the steps you attempt, and exactly the results of each step, most importantly the exact and complete content of any error messages presented.
Thanks and let us know!
Occam's Razor nearly always applies when troubleshooting technology issues!
If anyone has been helpful to you, please show your appreciation by clicking the button inside of their post. Please click here and read, along with the threads to which it links, for helpful information to guide you as you proceed. I always recommend that you treat your BlackBerry like any other computing device, including using a regular backup schedule...click here for an article with instructions.