(I don't good speak English sorry)

I have a problem with Ubuntu 8.04.
My system is suspended during copy files from local network and download updates. Mouse and keyboard (diodes blink) doesn't work. Helps only reset button.

My specification:
graphics: asus ati radeon 9600
RAM: kingston 512
CPU: AMD Sempron 1800+
motherboard: Epox 8k9a7i
WIFI: Gigabyte GN-WP01GS