Impossible to reinstall Gridcoin Wallet

This started yesterday when we had a power surge and lost power for about 2hours.

PC is fine and all hardware/software seem to work normally.
Except for the gridcoin wallet that wouldn't start.

I was on version 5.4.0. So I tried to upgrade with no luck. Got the message :

An old version is found on your system and will be uninstalled first to migrate registry entries and shortcuts. You wallet data will not be affected. Continue ?

After clicking yes and waiting hours, nothing happened. Restarted computer a few times, still not working.

I then started to backup my wallet and reinstall the whole thing following this steemit post.

Tried to reinstall and I still get the above message and installer crashes as soon as I click "Yes" (or "No" btw).

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Any help would be greatly appreciated!