Apple.DAV.Appointment cannot be opened. Comments please.

This problem began some time ago. I have seen others with "fixes" of deleting emails, recurring appointments, archival information, etc. which seem rather useless since they only seem to address the sympton & not the problem. Others have tried other things with limited success, if any. I have tried a lot of things as well. Setting my parameters out for others may help to identify where the problem actually is since both Apple & Microsoft both do not know how to fix this & keep throwing out try this; try that "solutions".

Consider that Outlook 2007 (which is my current email program) has not changed for a considerable time now (we are up to Outlook 2013 now) so if a reasonable assumption is made here, it is that Outlook 2007 is not the problem (consider that users of Outlook 2010 & Outlook 2013 report the same problem but not for earlier Outlook programs which indicates where the problem may be located).

Consider that I have been using Outlook 2007 right after Outlook 2003 with no problems like this until I got an iPhone & started trying to sync my Outlook 2007 to the iPhone (I had a Nokia 3120 which I was syncing with Outlook 2003 & Outlook 2007 with no problems other than those I created myself - & fixed.)

I originally set up iCloud but later discontinued using it since I was not convinced as to its security as well as the 5GB (I think) was really too small for a 16GB iPhone. Sometime after discontinuing iCloud & updating iTunes to 11.0.x version this problem began.

Since Apple seems to be the culprit in constantly making changes to their programs, I would suggest to Apple that the problem is theirs & maybe relates to their programs syncing with Outlook 2007, 2010, 2013 & that eliminating Outlook recurring appointments or old/archived info is not the problem. If this were the problem, I would suggest to anyone who has been "successful" in "correcting" the problem will, once again, encounter the same thing whenever they reach the conditions that prompted the issue in the first place (hence this is a fix for the symptom not a fix for problem conclusion).

My original OS for my computer (64bit) was Vista Professional (with all SP's). The problem noted here did not occur in Vista (I was also using the Nokia phone at the time). I upgraded to Windows 7 Home Premium (including SP1) during which time I switched from the Nokia to the IPhone (3g) with no problem (I believe that iCloud wasn't available to the time). I then switched to the iPhone 4 & after some time iCloud was introduced & somewhere along the time of the version 11.x.x for iTunes was introduced, this problem began for me.

Given the above, does anyone have any kind of logical explanation that could lead to a real solution rather than a fix. Obviously updating Outlook to 2010 or 2013 (or later?) is not the solution since all versions seem to encounter the same problem. Much as I don't care for Microsoft, I do not see (logically) that they are the problem in this.