Mustek 1200 USB scanner - help!

problems problems...

heres the deal. I had on old Acer parallel port scanner which i haven't used for an age but when i needed to use it (thru TWAIN in photoshop cs) recently it kept coming up with 'scanner not connected' even though it clearly was. i figured as it was old it had just died so this week bought a new scanner - a Mustek scanexpress 1200 USB plus...

although being boxed/new its an older model, coming only with win 98 drivers!(i'm on xp home sp2) - managed to track down the xp drivers on the net and got them installed (although the light on the scanner only comes on after doing the windows 'found new hardware' wizard) BUT...same as with the old Acer - when trying to scan in photoshop i get the same error message:

'Scanner is not connected please check the cable' followed by

'could not open TWAIN source, make sure there is a valid TWAIN source in the Windows directory'

looking in the windows twain directory, there is a Mustek 1200 folder in there with what looks like all the relevant files in it. theres also some other folders for my digital cameras/the old acer scanner etc. (i've tried it in different usb sockets too btw.)

any advice on this desperately needed as i've got loads of stuff that i need to scan for a job!

thanks in advance

c