I had this problem yesterday, i was a also a cloud, i went to advanced ettings and rebaked which transformed me into a half bald, white eyed, half naked avie wearing a ruth shape ( i didn't even know i posessed a shape called ruth! ), lol. It wouldn't let me wear or change anything because my inventory and shape was still downloading. When i opened my inventory, it was only showing just over 1,000 objects and i have over 25,000, i put the letter 'a' into the inventory search and it started loading more objects begining with 'a', i did this for each letter of the alphabet, it took a while, but eventually i had all of my items loaded. I then relogged and when i got back my inventory was working fine. Maybe this will work for you too. Good luck anyway!
I forgot to say i also use the phoenix viewer.