Error of App Close Main! During Start Up: You can fix the app close main error.. 1) Open 3rd Party Application like x-plore, Fexplorer. 2) Go to c:/system/bootdata & delete 'FirstBoot.dat'. 3) Turn off phone & take out your MMC card. 4) Turn on phone and put in current time/date. 5) Wait for it to boot up then turn off phone again. 6) Put MMC back in and turn on phone.