radeon v-card idle problem help, black screen when idle

[chillin29]

when ever i put it into sleep mode or let it idle for more then 15min. the screen will just go black while i can see my mouse cursor and be able to move it. when i press numlock or capslock no action, ctrl,alt,del no action. i have:

p3733
abit vh6 mobo
256mbpc133
sb live value
radeon 32ddr

with my geforce card it didn't have this prob.

thanks all...