htc android 4.0.3 unstable after upgrade how to reinstall?

[Android Question]

Model HTC Sensation Z710e
One plus year old. Before it had Android 2.3
I saw that an upgrade was available and attempted to do it. For a few days it worked. But now it is unstable and keeps reloading. There are messages sometimes about HTC Sense not working but these don't stay showing. Message System update is available is shown.
Currently on About phone I have:
s/w Android version 4.0.3
HTC Sense v 3.6
Model HTC Sensation Z710e
Browser WebKit/534.30

I can't do anything from this phone, like Software update.
I have installed HTC Sync on the PC but it says the phone is disconnected when I connect it.
How can I get it back to a stable situation?
Help gratefully received.

 

[quickaudi]

Welcome to the guest forums!

In upgrades, there are always one or two that don't go perfectly. I think yours might be one of them. I am recommending a factory reset of your phone. Under Settings - Backup and Reset - you are going to want to select Factory Data Reset. You will lose your data, but your apps and contacts should all be backed up to Google, but now would be a good time to confirm that before you reset your phone.

Resetting your phone will delete all data, including the data that got corrupted when you upgraded.

That should resolve your problem and give you a much better experience! Feel free to register for the forums and let us know how it goes!