Try this fix first: Without switching on your scanner, connect
it up to your pc first (usb or parallel). Then turn it on. Now
check if it detects and works.
If not, do the opposite, power on your scanner, then connect it
up.
Another if the above 2 does not apply, if your scanner feeds its
power off the comp via usb. Unplug the scanner, do a full reboot,
then plug it in.
Below is an alternative method, but since you mentioned you are
using photoshop CS, I don't think you want to heed it.
Download freeware irfanview from
http://www.irfanview.com/
Once done installing, open the app.
Under "File", select "Acquire", it will search for an available
scanner on your comp and start an interface to let you do your
scanning. 