what happened to make it blank out in the first place? cause if you haven't played with it using non-SE programs, then it *could* be somethign wrong with the phone
download FAR manager, and the plugin to make it work with SE phones.
(google for the links.) Then extract a custpack, and upload it to the phone (a generic one, unless you can figure out which was on your phone in the first place)
if you want to personalise it, just change files in the custpack before you upload it to your phone - but i'd stick to what you've got until you get your phone working again.may i personalize a file and how??