Keylogger(Stream Writer) is not working on Windows 8.1

Question

hello Experts,
I want to share my problem with you,
i developed a key logger in c# console based and windows form also its working fine,and also using stream writer to write a text file with keys.
i am using it on windows 7.8
and when i am moving to windows 8.1 then it partially blocked,
exe is running but not write keys to text,
means we can say stream writer is not working on windows 8.1

when i use my exe it was working sometime(When I make) but after around 1 hour stream writer not write keys in the text file.
my code/exe is f9 bcz i have tested it on windows 7,8.its working
any alternative of stream writer which i use on windows 8.1?
Pls suggest me...