I think it's now time for all the idiots who have problems with #SYS to dump their coins and leave the forum. (I bet they won't of course. They'll just come up with other excuses for complaining because they have no lives.)
Already dumped (at a loss), thanks for the advice... although I did wait for the new wallet, which was pretty underwhelming. And no, I'm not crying about it. C'est La Guerre.
But as a parting shot I'll offer a little advice to those with (windows) wallet issues. It won't solve them entirely (because it still falls over and corrupts the local blockchain), but it should sync.
Avoid The Installer.
This applies to a lot of coins after an upgrade. The installer leaves a ton of unnecessary shit in the registry, and you need to clean this out before installing a new version.
So, save your wallet in a secure place.
Run the installer, but DON'T run the wallet (qt) executable.
Have REVO Uninstaller, or a good alternative on your machine.
Copy the Upgraded QT (program) and DATA folders to a pen drive and remove it.
Run Revo at full strength to remove Every Trace of the coin from your machine.
Replace the program and data folders in their appropriate locations (you can choose these for yourself if you don't want to use the defaults).
Do Not Copy your wallet to the data folder.
Run the QT (it will create a new wallet).
Leave it to sync and download the blockchain.
Once you are happy that it's all in order, you can copy your working wallet to the data folder.
Alternatively use a clean system.
Make an image of the system drive "C:" using Acronis or one of the many excellent free imaging apps.
Install the wallet and make the copies as above.
Shut down your system and replace it with the clean image.
Fire Up and Restore the copied system and data folders to their appropriate locations. Proceed as advised above.
Alternative 2 is a method I use regularly to ensure a clean and virus-free environment. It's not as daunting as it seems if you include trusted software in the image, and employ a decent strategy to perform upgrades on a clean copy and then upgrade the image. I usually start with a backup of my current system (for a quick restore in case of problems), replace it with the most recent image, upgrade my software, drivers etc. and then make a new image before starting to use the upgraded system.
But i digress...
Goodbye and good luck. Encourage someone tech savvy to try my methods and report back with more detailed procedures.