Can't boot up, the smartphone's stuck in an endless reboot cycle!

A. This sounds like something you've installed is causing the problem. If you tend to install most applications to your expansion card, try removing the card and rebooting again. Does it work now? Insert the card again. Look for the culprit in a utility that's set to auto-start - remove it (e.g. in Tools | Manager) and try rebooting again. Hopefully, the problem's solved.

If your device still won't boot, even without your expansion card in place, then it's something on your internal disk. I'd recommend wiping this disk (using the usual Green+*+3 press while powering on), checking things work and then restoring from your last PC Suite backup of the internal disk (or simply syncing across your info again).