My workunits end in few seconds.
This time I am using Microsoft Security Essentials and already added folders related to WUProp@Home to exclusion lists.

Screenshots of MSE(texts are in Japanese):
excluded files and places
excluded kinds of files
excluded processes

What should I do to solve this problem?

My PC specs:
Windows Vista Home Premium SP2 32bits
Intel(R) Core(TM)2Duo T8100 @2.10GHz 2.10GHz
RAM 4.00GB

A workunit started to work properly (not ending in 5 minutes) now.
I wonder whether this means the problem is solved or this is only tempolary happening.
I also wonder what divides working and not working workunits.
It started to work properly when a task from Collatz Conjecture finished its calculation and tried to upload the result (unfortunately, the upload failed due to server problem).