Norton caused my PC to crash and lag, now I've lost subscription

So I've recently bought a 1-year subscription (3 PCs) and have used it on 3 PCs for Norton Internet Security 2014. Yesterday my main PC started packing up, and crashed several times. At the time I thought it was due to overheating, left it over-night, and thought nothing more of it. After waking up this morning, and attempting to switch on my PC I was confronted with an extremely slow system start-up, program load, and generally the OS freezing.

I ran several diagnostics thinking it was to do with registry files, etc. but was surprised to see a Norton errorbox pop-up suddenly. It began scanning its own files, but couldn't tell me the reason behind all the problems. I tried opening Norton to run a system scan (for viruses, which might have been a cause of the crashing, etc.) but it refused to open. At this point I started investigating online, and found that Norton had been updated from Internet Security 2014 to the newest version Norton Security. It appeared that the update had been causing my system to crash for some reason (even though I was never aware Norton was attempting to update!), so I had to use the Norton Removal Tool to wipe any existing files from my PC in order to clear this problem. After doing so, my PC runs fine - no crashes or lag so far! - but in the instructions for the Removal Tool it said after system restart Norton would restart itself so as to give me the updated version (presumably with the remainder of my subscription - about 10 months).

Nothing happened upon restart, so I had to manually download the trial version. When I entered the same Product Key as I had used for Norton Internet Security 2014 on my main PC it told me that there were no subscriptions left from this purchase. So effectively I seem to have lost 10 months worth of subscription due to an error in a Norton update. Is there any way to recover the subscription, as currently I have 30days left on the trial edition. If I've done anything wrong can someone let me know, so that I can fix it.

Sorry for the long post, and hopefully I can get this resolved without having to dig into my own empty pockets again. Thanks