My Blackberry Curve 8520 wont start up, need help!!!?

Basically, my Blackberry froze, so as i usually do i left it 20 minutes for a response, then removed the battery and put it back in, now when the screen comes up to load it, the white bar goes just over half way and doesnt move from there it stops just under the 'e' in blackberry. i have tried taking the sim, micro sd, and both and restarting it and it doesnt work, i have also tries plugging it in to my laptop and using blackberry desktop, but it just wont load. can someone help me please? ps. my phone has done this before but it finally started again after an hour, it has now been 3 and it hasnt done anything.