Wipe the BB AFTER doing a backup and restore your data.
You can upgrade the OS or at least clean it up at the same time.
Once your running then try Appworld. Be careful and do only one app at a time and maybe you will find the one causing issues. I would suspect one app is not for your model.
How to wipe ALL personal data from a BlackBerry device? - BlackBerryFAQ
How do I upgrade the OS on my BlackBerry? - BlackBerryFAQ