Hi gavros777.
Is this happening with any other game? Are your graphic drivers up to day?
If after updating your drivers, if you're still experiencing this issue, please create a support ticket HERE. Please ensure to provide a DxDiag and MSINFO of your system and our Support Team will be happy to look into this for you.
Thanks.
I too am having what appears to be a driver related issue or at least a lock up. It happens every time I play the game for more than hour. The OS says the game is not responding and takes about 15+ seconds to get to the desktop to end the game. I do not have this problem with Far Cry 3 or XCOM. Here's the info from DxDiag
Operating System: Windows 7 Professional 64-bit (6.1, Build 7601) Service Pack 1 (7601.win7sp1_gdr.150427-0707)
Language: English (Regional Setting: English)
System Manufacturer: OEM
System Model: OEM
BIOS: Phoenix - AwardBIOS v6.00PG
Processor: Intel(R) Core(TM) i7 CPU 920 @ 2.67GHz (4 CPUs), ~3.8GHz
Memory: 12288MB RAM
Available OS Memory: 12280MB RAM
Page File: 3621MB used, 20934MB available
Windows Dir: C:\Windows
DirectX Version: DirectX 11
DX Setup Parameters: Not found
User DPI Setting: Using System DPI
System DPI Setting: 96 DPI (100 percent)
DWM DPI Scaling: Disabled
DxDiag Version: 6.01.7601.17514 64bit Unicode
Operating System: Windows 7 Professional 64-bit (6.1, Build 7601) Service Pack 1 (7601.win7sp1_gdr.150427-0707)
Language: English (Regional Setting: English)
System Manufacturer: OEM
System Model: OEM
BIOS: Phoenix - AwardBIOS v6.00PG
Processor: Intel(R) Core(TM) i7 CPU 920 @ 2.67GHz (4 CPUs), ~3.8GHz
Memory: 12288MB RAM
Available OS Memory: 12280MB RAM
Page File: 3621MB used, 20934MB available
Windows Dir: C:\Windows
DirectX Version: DirectX 11
DX Setup Parameters: Not found
User DPI Setting: Using System DPI
System DPI Setting: 96 DPI (100 percent)
DWM DPI Scaling: Disabled
DxDiag Version: 6.01.7601.17514 64bit Unicode
I can email the txt file if you wish to see more info.