What do you mean the "gmail storage application?" I am having the same problem with my gmail not opening. It says, "loading conversations". I tried turning the phone off and back on but the same message it there when I open the gmail tab. Thanks for any advice.
You clear the data by going to your phone settings > manage applications > applications > all. Scroll down to listing for gmail and select it to open the view. There will be a button called clear data there that you press. Back out to all view. Then you would repeat the same process for the listing for gmail storage if your phone has it.