I had the same problem...and then I installed updates for my OS version...and it worked...You should be able to upload any themes. This problem appears to happen a lot...I found my solution here....it doesn't list your phone model but it may explain depending on the version of desktop software your running.
CrackBerry is in no way Affiliated with BlackBerry. We take pride in our unbiased content, however do occasionally receive free products from vendors that we review or discuss. For more info click here.