Can't sync iTunes 11.4 with iOS 7.1.2?

Hi, not sure if there is already a thread on this but I have tried a search.

I have just upgraded my iTunes to 11.4 and now neither my iPad Air or iphone 5 (both on iOS 7.1.2) will sync.

They both appear in iTunes and I can access the tabs and check/uncheck music ect but the sync button is greyed out. I have tried the back up button and making a change then hitting 'apply' but both start to sync then stop after about a 2 seconds with no error message.

The usage bar at the bottom just shows everything on my devices in the yello 'other' category.

I have downloaded the ios8 update for both devices but neither will run as I just get an error saying that iTunes cannot back up the device after the software has been extracted and it then stops.

Any help would be appreciated, I can't understand why I can no longer sync either device.

Many thanks.

I did try restarting etc. However after a bit of googling it appears that the new iTunes (and so now iphone 6) isn't supported by older machines-I have a 1st gen MBP.

Not sure if this is ok but not great if it is as I can't justify the best part of £1000 for a new machine and in all other ways my MBP is working perfectly.

I have moved my iTunes account to my wife's desktop (a more recent iMac) and all works fine. Just a pain not being able to sync my phone or upgrade to an iPhone 6 with my own laptop.