Unfortunately, there's no good answer without using the "U" word in reference to your Exchange Server. Mainstream Support for Exchange 2003 ended 4/14/2009. Extended support is available from Microsoft until 4/8/2014, but the way ActiveSync functions was changed with the advent of Exchange 2007 and again with 2010. Apple simply had to keep up with things.
The BB generally doesn't sync directly with Exchange. They insert their service in the middle, which takes care of things like this.
Firstly, apologies for the slow response to your very quick reply !
I've checked back, we're using Exchange 2007.
We've actually got a ticket open with Apple at present, so anticipate that a patch may be available.
It is still curious though that out of a 200 user community trialling our internal iPhone & iPad pilot, we only have 2 issues (mine and a colleagues), however anticipate that there will be more issues as nearly entire community is on 5.1.1.
On a second point, any ideas how one can rollback to 4.3.3 on an iPhone or iPad ? I can't find anything that implies a self rollback without jail breaking the device ?
Thanks again for the help.