It is very strange. 1 out of 20, I will have successful results. But 19 out of 20 will failed with No CUDA devices found (Will attach output in second post)

<core_client_version>7.0.28</core_client_version>
<![CDATA[
<stderr_txt>
setiathome_CUDA: Found 1 CUDA device(s):
Device 1 : GeForce GT 640
totalGlobalMem = 1073741824
sharedMemPerBlock = 49152
regsPerBlock = 65536
warpSize = 32
memPitch = 2147483647
maxThreadsPerBlock = 1024
clockRate = 954000
totalConstMem = 65536
major = 3
minor = 0
textureAlignment = 512
deviceOverlap = 1
multiProcessorCount = 2
setiathome_CUDA: CUDA Device 1 specified, checking...
Device 1: GeForce GT 640 is okay
SETI@home using CUDA accelerated device GeForce GT 640
setiathome_enhanced 6.09 Visual Studio/Microsoft C++
libboinc: 6.3.22

Work Unit Info:
...............
WU true angle range is : 0.362006
Optimal function choices:
-----------------------------------------------------
name
-----------------------------------------------------
v_BaseLineSmooth (no other)
v_GetPowerSpectrum 0.00016 0.00000
v_ChirpData 0.00919 0.00000
v_Transpose4 0.00295 0.00000
FPU opt folding 0.00247 0.00000

Flopcounter: 56663637304666.953000

Spike count: 11
Pulse count: 3
Triplet count: 0
Gaussian count: 0
called boinc_finish

</stderr_txt>
]]>