Iphone 5s & outlook 2003 syncing results"irregular"

before I had no syncing problems between my iPhone 4 / iTunes / outlook 2003, on my windows 8 pc.

I recently changed to an iPhone 5s

in the beginning it synced just fine, but then the results started to be very irregular for all items (contacts, calendar, notes):

sometimes they would sync, sometimes not..

Then it stopped altogether, so I decided to completely re-install iTunes & this worked

for about 2 days and then stopped again.

(Strangely enough sometimes a hard-reboot of the iPhone would fix it for 1 sync)

I again re-installed ITunes, and this time noticed that the FIRST time I synced all went well, but each time there after: NOTHING.

Completely at loss as to why sometimes it works & most of the time not...?