UPDATED ans SOLVED a re-install fixed my problem, so feel lucky

If your have had a similar problem read on.
I got this error message when trying to load a saved game "Player prototype required but missing", then on clicking "ok" on the message the game shuts down.
Any ideas?

Did not think I need a screen shot; it was a separate window that pops up. I have a backup of my save, yet same problem there.
Thankful for any tips

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System Information
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Operating System: Windows 8.1 Pro 64-bit (6.3, Build 9600) (9600.winblue_gdr.131030-1505)
Language: Swedish (Regional Setting: Swedish)
System Model: P67A-UD4-B3
BIOS: Award Modular BIOS v6.00PG
Processor: Intel(R) Core(TM) i7-2600K CPU @ 3.40GHz (8 CPUs), ~3.7GHz
Card name: NVIDIA GeForce GTX 580
Memory: 8192MB RAM
Available OS Memory: 8176MB RAM
Page File: 3460MB used, 12906MB available
DirectX Version: DirectX 11
System DPI Setting: 96 DPI (100 percent)
DWM DPI Scaling: Disabled
DxDiag Version: 6.03.9600.16384 64bit Unicode