iPhone 3G black screen with respringing circle.

[FredCompany]

I have an iPhone 3G 8GB, with iOS 4.2.1 (I have no idea what baseband) It's factory unlocked, and the SIM inside it is a "3" one. It's jailbroken and has a lot of tweaks installed (Five Icon Dock, AndroidLock, MyOS, to name but a few)

Recently I've been having problems. The sleep and volume buttons often stop working, mostly while playing music (although that could be a coincidence, as I mostly use it for playing music). Also, every now and then (once a week or so) it decides there's no SIM card installed, and I have to remove it and put it back in for it to be recognised. iTunes recognises it until I try to sync, and then ejects it.

Last week I had a camping trip (And trips to the beach) during which time, to save power I did a force reset (sleep and home buttons pressed and held) after I had checked Twitter and Facebook, about 5 times. I doubt it got sand in it, but it's a possibility.

After the trip it randomly freezes and crashes, exiting whatever app I'm in, showing the home screen, and after a bit, showing the respringing wheel in the centre. It stays like this until I do a force reset. It crashes a lot, especially:

• After about a minute of inactivity (possibly when the auto-lock activates)
• If, after exiting an app, I press the sleep button straight away
• Other, seemingly random, times

The last time it crashed was after I ended a call (Gmail confirmation call). It got stuck on the "Accept or Decline call" screen, and eventually went to a black screen. Force resets won't work (and neither will mashing all the buttons), and it doesn't do the usual "double-vibrate" when charging. iTunes still won't recognise it, and on my dad's Windows computer it says "Installing device driver software" and then a failure message of some kind.

Any ideas on how I can restore/downgrade it and get it working again?

[iYeow]

If restoring to stock firmware of 4.2.1 doesn't solve your issue, then you have a hardware problem.

[FredCompany]

I can't restore, because iTunes isn't recognising the phone. It might just be my cable though, so I'll try with a new cable and report back.