xserver problem - hang

Dear
When I restart the Xserver it works fine for less than half an hour and throw this error afterward.

After setting the display DISPLAY=10.195.2.13:0.0, I tried to run xclock. After few minutes it throws this error message

"X connection to 10.195.2.13:0.0 broken (explicit kill or server shutdown)"

That mean Xvfb is not stable on the O/S. How to resolve this problem?

Thanks
Mohammed Tanvir