"Cooling jars
When you remove hot jars from a canner, do not retighten their jar lids. Retightening of hot lids may cut through the gasket and cause seal failures. Cool the jars at room temperature for 12 to 24 hours. Jars may be cooled on racks or towels to minimize heat damage to counters. The food level and liquid volume of raw-packed jars will be noticeably lower after cooling. Air is exhausted during processing and food shrinks. If a jar loses excessive liquid during processing, do not open it to add more liquid. Check for sealed lids as described below.

Testing jar seals
After cooling jars for 12 to 24 hours, remove the screw bands and test seals with one of the following options: Option 1. Press the middle of the lid with a finger or thumb. If the lid springs up when you release your finger, the lid is unsealed.
Option 2. Tap the lid with the bottom of a teaspoon. If it makes a dull sound, the lid is not sealed. If food is in contact with the underside of the lid, it will also cause a dull sound. If the jar is sealed correctly, it will make a ringing, high-pitched sound.
Option 3. Hold the jar at eye level and look across the lid. The lid should be concave (curved down slightly in the center). If center of the lid is either flat or bulging, it may not be sealed."

you might want to look at the diagrams accompanying this quotations at the following link:

http://www.uga.edu/nchfp/how/general/cooling_jars_test_seals.html

My best guess (actually its from the problem solving section in the back of the book p. 424 ;) is

1) the fruit wasn't heated through thoroughly before packing
2) jars were over-packed.
3) air bubbles not removed sufficiently
4) screw bands applied too loosely

Thorough heating in the syrup will remove most of the air from the slices and then they don't float near as much but we often get in a hurry and this is a common source of problems.

But the headspace allotment is best measured after the syrup is added and yes, with the apples floating. Did you still have the "generous 1/2"+ at that point?

See where it says "remove air bubbles and adjust headspace"? Sometimes you have to remove a slice or 4 to get the spacing just right.

As to what to do with them - all I can tell you is what I would do. After 12 hours do like Ken suggested and check the seals very carefully. If all are good seals then remove the bands and wash the jars thoroughly to remove all the boilover syrup - especially the threads of the jars. You can then freeze, refrigerate if you have the room, or if not, then date & mark the jars with whatever mark you use for questionable jars (I use black X) and store them normally. The mark reminds me to take extra care with them when opening.

If any of the seals are weak - reheat contents thoroughly and reprocess with clean jars and lids.

Hope this helps. Good luck! ;)

Dave

before you decide to freeze, are the apples in a freeze/can jar, ie, straight sides? they'll expand when frozen and could pop the top or crack the jar particularly if it's one of the shouldered jars. You'll also want to be sure you have at least the full 1/2+" headspace to allow for expansion.

if the jars are not sealed and you wish to freeze rather than reprocessing, you'll want to put the ring back on. I'd use a new flat or use one of the plastic 1-piece lids. It might be best to transfer to a rigid-side freezer container.

I'm sorry you had these problems, but you have inadvertently helped me, since I had planned to use that recipe this week ... now I know what to watch out for.
-kay