[Q] Exchange on ICS with PIN protection - Sony Xperia P, U, Sola, Go

Does anyone else have any problems using the native mail client with Exchange?
Our company have (finally) enabled ActiveSync, with Android formally 'supported'
However, when I enter the details, it tells me the 'Server requires unsupported security features'
Indeed, we have to assign a 4-digit PIN to our account, but whilst it works fine for my fellow colleagues on Android, it doesn't for me!
But... if I use, say Moxier Mail, it works fine - I'd just rather use the native client!
I even read somewhere than having apps installed from sources other than PLAY could cause this, but I've uninstalled the only such app with it making no difference
Could it have anything to do with the fact I manually upgraded to ICS rather than OTA - or is it really as basic as Sony's implementation doesn't cater for the requirement to have a pin code?
Edit:
Ok, so I have the same issue with my Sony tablet. But, with my wife's Samsung Galaxy Ace + it's works perfectly.
So it's either a Sony thing, or maybe an ICS thing?
When I load up the Security Policies option from Touchdown (yep, works here too!), it gives the below - is there really anything in there is out of the ordinary?
- Allow Simple Password? No
- Alphanumeric Password
- Min Complex 1
- Password/PIN required
- Failed Attempts 4
- Min Length 4
- Timeout 120 sec.
- Expires 90 days
- History 8 entries
- Password Recovery
- Max Email download Size - 5120
- Email History 7 days
- Calendar history 30 days