Ok, I´ve changed to BitDefender and now without any problems too, adios Norton.

I noticed some artifacts with the ssao effects (look at this video - Please wait a little!)

http://www.public.gamefactor.eu/shadec_ssao.swf

My specification:

FPS (~150 -> ~180)

Operating System
Windows System : Microsoft Windows Vista Ultimate 6.00.6001 (Service Pack 1)
Platform Compliance : x86

Processor
Model : Intel(R) Core(TM)2 Duo CPU E8400 @ 3.00GHz
Speed : 3GHz
Cores per Processor : 2 Unit(s)
Threads per Core : 1 Unit(s)
Type : Dual-Core
Internal Data Cache : 2x 32kB, Synchronous, Write-Thru, 8-way, 64 byte line size
L2 On-board Cache : 6MB, ECC, Synchronous, ATC, 24-way, 64 byte line size, 2 threads sharing

System
System : Gigabyte Technology Co., Ltd. EP35-DS3P
Mainboard : Gigabyte Technology Co., Ltd. EP35-DS3P
Bus(es) : PCI PCIe IMB USB FireWire/1394 i2c/SMBus
Multi-Processor (MP) Support : Yes
Multi-Processor Advanced PIC (APIC) : Yes
System BIOS : Award Software International, Inc. F2
Total Memory : 4GB DIMM DDR2 DDR3

Chipset
Model : Giga-Byte P35/G33/G31 Processor to I/O Controller
Front Side Bus Speed : 4x 333MHz (1.33GHz)
Total Memory : 4GB DIMM DDR2 DDR3
Memory Bus Speed : 2x 400MHz (800MHz)

Memory Module(s)
Memory Module : Corsair CM2X2048-6400C5DHX 2GB DIMM DDR2 PC2-6400U DDR2-800 (5.0-5-5-18 3-22-6-3)
Memory Module : Corsair CM2X2048-6400C5DHX 2GB DIMM DDR2 PC2-6400U DDR2-800 (5.0-5-5-18 3-22-6-3)

Video System
Adapter : NVIDIA GeForce 9800 GTX/9800 GTX+ (512MB DDR3, 625MHz/1.45GHz/2x1.10GHz, PCIe 1.00 x16, SM4.0)

Graphics Processor
Adapter : GeForce 9800 GTX/9800 GTX+ (1.01, 512MB, 1.69GHz)

Thanks again