Failure of the screen to enter sleeping mode

[jar022855]

Hello Before I wrote this post I reviewed the many posts on this topic,but I failed to find any solutions. I hope it was an oversite on my part.
The problem is that when the screen would be anticipated to go into hybernation,I hope that's the right term,the screen goes black with white technical writing that is uninterpetable to me. The screen is absolutely frozen. All efforts to reboot are in vain save turning the computer off,then rebooting which I'm told is deleterious to the health of the computer.
This is occuring on an other "healthy" IBM Netvista Pentium 4 CPU 180 Ghz,memory 1500 MB with Linux Mint 12 LXDE installed
When I used the same cd to install Mint in a Dell Dimension 5310 I have had no problem.
with graditude,Norman Eisenstadt