I got this problem when first get my P535 from O2 zone. It always hang and the wifi option is gone too. The manual said that wifi and usb cannot be used together. So, most of the time, wifi is gone after connect to pc via usb. I end up very frustrated and hard reset the device, install everything manually, then both problem solved. It might be installation problem at the shop or incompatible applications, but I'm not sure.