Thakns for your input. They are kernel panics, grey screen, reboot et al. I am not sure this is the appropriate log (copied from Console/DiagnosticReports) but here it is:
Fri Nov 1 12:47:50 2013
panic(cpu 0 caller 0xffffff800acdc19e): Kernel trap at 0xffffff80482d0b20, type 14=page fault, registers:
CR0: 0x000000008001003b, CR2: 0xffffff80482d0b20, CR3: 0x000000000d83b000, CR4: 0x00000000001606e0
RAX: 0xffffff800ac4cb10, RBX: 0xffffff804a2b7280, RCX: 0xffffff804a2b7280, RDX: 0xffffff804a2b73c8
RSP: 0xffffff839b34bec8, RBP: 0xffffff800b2fcbb8, RSI: 0x0000000000000000, RDI: 0xffffff800b2cb788
R8: 0x0000000000000000, R9: 0x0000000000000000, R10: 0x00000000ffffffff, R11: 0xffffff7f8b904516
R12: 0xffffff800b2d2ab8, R13: 0xffffff804a2b7280, R14: 0xffffff800b201814, R15: 0xffffff839b34bee0
RFL: 0x0000000000010096, RIP: 0xffffff80482d0b20, CS: 0x0000000000000008, SS: 0x0000000000000010
Fault CR2: 0xffffff80482d0b20, Error code: 0x0000000000000011, Fault CPU: 0x0 Kernel NX fault
Backtrace (CPU 0), Frame : Return Address
0xffffff839b34bb50 : 0xffffff800ac22f69
0xffffff839b34bbd0 : 0xffffff800acdc19e
0xffffff839b34bda0 : 0xffffff800acf3606
0xffffff839b34bdc0 : 0xffffff80482d0b20
0xffffff800b2fcbb8 : 0x0
BSD process name corresponding to current thread: kernel_task
Mac OS version:
13A603
Kernel version:
Darwin Kernel Version 13.0.0: Thu Sep 19 22:22:27 PDT 2013; root:xnu-2422.1.72~6/RELEASE_X86_64
Kernel UUID: 1D9369E3-D0A5-31B6-8D16-BFFBBB390393
Kernel slide: 0x000000000aa00000
Kernel text base: 0xffffff800ac00000
System model name: iMac14,2 (Mac-27ADBB7B4CEE8E61)
System uptime in nanoseconds: 1908156512798
last loaded kext at 1534976300436: com.apple.driver.AppleUSBCDC 4.2.1b2 (addr 0xffffff7f8d196000, size 20480)
last unloaded kext at 1698286160841: com.apple.iokit.IOUSBMassStorageClass 3.6.0 (addr 0xffffff7f8bba9000, size 69632)
loaded kexts:
com.apple.driver.AppleBluetoothMultitouch 80.14
com.apple.driver.AudioAUUC 1.60
com.apple.driver.AppleHWSensor 1.9.5d0
com.apple.filesystems.autofs 3.0
com.apple.iokit.IOBluetoothSerialManager 4.2.0f6
com.apple.driver.AGPM 100.14.11
com.apple.driver.ApplePlatformEnabler 2.0.9d1
com.apple.driver.X86PlatformShim 1.0.0
com.apple.driver.AppleMikeyHIDDriver 124
com.apple.driver.AppleHDA 2.5.2fc2
com.apple.driver.AppleUpstreamUserClient 3.5.13
com.apple.iokit.IOUserEthernet 1.0.0d1
com.apple.GeForce 8.1.8
com.apple.driver.AppleIntelHD5000Graphics 8.1.8
com.apple.driver.AppleMikeyDriver 2.5.2fc2
com.apple.iokit.BroadcomBluetoothHostControllerUSBTransport 4.2.0f6
com.apple.driver.AppleThunderboltIP 1.0.10
com.apple.driver.AppleLPC 1.7.0
com.apple.driver.AppleSMCLMU 2.0.4d1
com.apple.driver.AppleIntelFramebufferAzul 8.1.8
com.apple.Dont_Steal_Mac_OS_X 7.0.0
com.apple.driver.AppleHWAccess 1
com.apple.driver.AppleBacklight 170.3.5
com.apple.driver.AppleMCCSControl 1.1.12
com.apple.AppleFSCompression.AppleFSCompressionTypeDataless 1.0.0d1
com.apple.AppleFSCompression.AppleFSCompressionTypeZlib 1.0.0d1
com.apple.BootCache 35
com.apple.driver.AppleUSBHub 650.4.4
com.apple.driver.XsanFilter 404
com.apple.iokit.IOAHCIBlockStorage 2.4.0
com.apple.driver.AppleSDXC 1.4.0
com.apple.iokit.AppleBCM5701Ethernet 3.6.9b9
com.apple.driver.AirPort.Brcm4360 800.21.45
com.apple.driver.AppleAHCIPort 2.9.5
com.apple.driver.AppleUSBXHCI 650.4.3
com.apple.driver.AppleACPIButtons 2.0
com.apple.driver.AppleRTC 2.0
com.apple.driver.AppleHPET 1.8
com.apple.driver.AppleSMBIOS 2.0
com.apple.driver.AppleACPIEC 2.0
com.apple.driver.AppleAPIC 1.7
com.apple.nke.applicationfirewall 153
com.apple.security.quarantine 3
com.apple.driver.AppleMultitouchDriver 245.13
com.apple.driver.AppleBluetoothHIDKeyboard 170.15
com.apple.driver.IOBluetoothHIDDriver 4.2.0f6
com.apple.driver.AppleHIDKeyboard 170.15
com.apple.kext.triggers 1.0
com.apple.iokit.IOSerialFamily 10.0.7
com.apple.driver.DspFuncLib 2.5.2fc2
com.apple.vecLib.kext 1.0.0
com.apple.iokit.IOAudioFamily 1.9.4fc11
com.apple.kext.OSvKernDSPLib 1.14
com.apple.iokit.IOAcceleratorFamily 98.7.1
com.apple.nvidia.driver.NVDAGK100Hal 8.1.8
com.apple.nvidia.driver.NVDAResman 8.1.8
com.apple.iokit.IOSurface 91
com.apple.iokit.IOBluetoothHostControllerUSBTransport 4.2.0f6
com.apple.iokit.IOBluetoothFamily 4.2.0f6
com.apple.driver.AppleThunderboltEDMSink 1.2.1
com.apple.iokit.IOAcceleratorFamily2 98.7.1
com.apple.AppleGraphicsDeviceControl 3.4.12
com.apple.driver.AppleHDAController 2.5.2fc2
com.apple.iokit.IOHDAFamily 2.5.2fc2
com.apple.driver.AppleSMBusPCI 1.0.12d1
com.apple.driver.X86PlatformPlugin 1.0.0
com.apple.driver.AppleSMC 3.1.6d1
com.apple.driver.IOPlatformPluginFamily 5.5.1d27
com.apple.driver.AppleBacklightExpert 1.0.4
com.apple.iokit.IONDRVSupport 2.3.6
com.apple.driver.AppleSMBusController 1.0.11d1
com.apple.iokit.IOGraphicsFamily 2.3.6
com.apple.driver.AppleUSBMergeNub 650.4.0
com.apple.driver.AppleThunderboltDPOutAdapter 2.5.0
com.apple.driver.AppleThunderboltDPInAdapter 2.5.0
com.apple.driver.AppleThunderboltDPAdapterFamily 2.5.0
com.apple.driver.AppleThunderboltPCIDownAdapter 1.4.0
com.apple.iokit.IOSCSIArchitectureModelFamily 3.6.0
com.apple.driver.AppleUSBComposite 650.4.0
com.apple.driver.CoreStorage 380
com.apple.iokit.IOUSBUserClient 650.4.4
com.apple.driver.AppleThunderboltNHI 1.9.2
com.apple.iokit.IOThunderboltFamily 2.8.5
com.apple.iokit.IOEthernetAVBController 1.0.3b3
com.apple.iokit.IO80211Family 600.34
com.apple.driver.mDNSOffloadUserClient 1.0.1b4
com.apple.iokit.IONetworkingFamily 3.2
com.apple.iokit.IOAHCIFamily 2.6.0
com.apple.iokit.IOUSBFamily 650.4.4
com.apple.driver.AppleEFINVRAM 2.0
com.apple.driver.AppleEFIRuntime 2.0
com.apple.iokit.IOHIDFamily 2.0.0
com.apple.iokit.IOSMBusFamily 1.1
com.apple.security.sandbox 278.10
com.apple.kext.AppleMatch 1.0.0d1
com.apple.security.TMSafetyNet 7
com.apple.driver.AppleKeyStore 2
com.apple.driver.DiskImages 371.1
com.apple.iokit.IOStorageFamily 1.9
com.apple.iokit.IOReportFamily 21
com.apple.driver.AppleFDEKeyStore 28.30
com.apple.driver.AppleACPIPlatform 2.0
com.apple.iokit.IOPCIFamily 2.8
com.apple.iokit.IOACPIFamily 1.4
com.apple.kec.corecrypto 1.0
com.apple.kec.pthread 1