Edit of a doc I published back in early Oct 2012. This is now fixed by using IOS 6.0.1.
New edit. Looks like IOS 6.1 and exchange do not play well together!
This happened earlier in the week, when it appeared i had cancelled a meeting , when in fact i had been nowhere near the invite except accepting it, some weeks ago. This was also not my invite, therefore i have no way (usually) of cancelling it !
So with this odd behaviour i thought no more until one of my key suppliers sent me the following today. They are a big firm with many idevices of varying ages, etc. I also have to assume a company of this size will be taken seriously by both Microsoft and Apple. Please read the release below:
IT continues to investigate the Apple iOS 6 calendar issues outlined below, and we are working with Apple and Microsoft to resolve the problem. Because there is no change at this point, you should continue to handle meeting invitations using your PC or Mac instead of your iPhone or iPad. There is no estimated resolution date. IT will continue to update you in the meantime.
We have learned that the new Apple iOS 6 has caused intermittent and inadvertent deletion of Outlook meetings from calendars. This is a global issue not specific to us, but we have received several reports of calendar items being deleted from our calendars. The issue at times occurs intermittently when a meeting is sent to a DL, and a user who has upgraded to Apple’s iOS 6 (either via an iPhone 5 or by upgrading a current iPhone) deletes the meeting. The meeting appears to have been cancelled by the person who deleted the meeting, who now appears to be the meeting’s organizer. This has also occurred without any user actions.
We have elevated this issue with both Microsoft and Apple but there is currently no resolution. Both software vendors are suggesting that users only handle meeting invitations using their PCs or Mac Outlook clients, versus managing appointments on your iOS device (iPhone and/or iPad) for the time being. We will continue to provide updates every morning until there is a resolution.
So there you go, leave alone your idevice if you want to manage your day. Along with maps, this is rough ride time for Apple.
Update 16/10/2012. This has no fix in sight, and Apple and MS are still saying use outlook and don’t manage your diary using your £500 phone. Amazing !

UPDATE: 06/12/2012. This apparently has been fixed by an update in IOS update 6.0.1 Currently in testing.
UPDATE: 18/02/2013. OS testing obviously not a hot spot for Apple right now. Apparently IOS 6.1 causes Exchange 201 to misbehave and in extreme circumstances stop working. Not mentioned in the link is the fact that apparently 6.1.1 is not the fix, as that just for batteries on the 4S. Madness. More new here :