IPhone – Find My Friends Settings

Firstly I would sign up to iCloud if you haven't and then use the over the air backup to backup your iPhone (You get 5GB free!) then once this is done, you will be able to reset the phone should you want / need to.

Have there been any updates to your Virtual Box since your last sync? If not, it could be that iTunes can not see its XML file needed for device synchronisation; also ensure that all of the helper services are started on your machine.

Failing the above and assuming you follow the first recommendation, try resetting and restoring from iCloud.

Best of luck

If you go to Settings > Mail, Contacts, Calendars > iCloud (should be the first account) and scroll down to Contacts.

When you scroll to "Contacts" you must slide it off. I did this by sliding the "Contact" button from right to left and swiped away the green. I was prompted to "What would you like to do with the previously synced iCloud contacts on your iPhone. I chose "Keep on My Phone".

Then you can use iTunes like you used to do and select the Contacts you want to be synced. I prefer this way.