need help with black screen (virgin mobile)

hey guys i sorta need some help here lol and ima total noob at this. so at first i used SWupgrade to install inxane and then recovery and then i backed system and data up. then i wanted to install a custom rom right and so i wipe/factory reset the phone and then i installed basic rom 1.7 so when i rebooted phone it was blackscreen so then i tought oh i must've messed up so then i decided to try to go back to stock so i can get things to work again. so then i wipe/factory reset and loaded stock rom and stock backup and that ended up in blackscreen again. so i searched over in sdx developers and i found a fix which i tried... first i deleted /data and /system and then reloaded the system_virginmobile.tar and that got me past the blackscreen and the phone worked fine for a about 30-45 mins and then it went to blackscreen. the exact things i did when the phone worked was send a few txt messages checked if my calling works and then i went on the internet and typed in google with the keyboard slided open...after the phone went to google.com i slid the keyboard down and the phone automatically shutted down and when i tried to turn it back on i get the samsung mobile page and then i get the virgin mobile logo thingy and then after that it just went back into blackscreen. is there anything i can do? thanks for any help u can give me