Mustek 2400 installation

Hi

Have just purchased a Mustek ScanExpress A# USB 2400 Por and cant seem to install it. I'm on a 2.4ghz imac running 10.6.8. I'm on image acquire, have installed the drivers for this os, the scanner name appears in the ImageAcquire drop down box, but when i click on it it says scanner not connected. I know the scanner works because i took it into work and tried it on a similar system and it worked. Any hints ot there on why it's not talking to my mac?

Thanks