Airport express wont/cant join network??

Hi,

Im running a white 24" imac, internet via airport extreme and cable,virgin media i connect via the airport card built into the imac. Never had any problems with this setup, i also have an apple tv which syncs with no problems.

For christmas my GF bought me an airport express so i can play itunes on our kitchen hi-fi.

However, i can't get the express to get beyond the flashing amber light, ive tried plugging it directly into the cable modem, flashing amber light, tried plugging into the extreme, still an amber light!

When i first connected the express it was picked up in the Airport Utility, knocked out my net settings and hasn't been picked up since!

whilst trying to install via the software i keep getting these messages,

'In order to use the AirPort Setup Assistant your AirPort card must be enabled and AirPort needs to be turned on and set to use DHCP. Click OK if you would like to change these settings, or Skip if you would like to configure AirPort Base Stations using ethernet'

soon followed by this,

'There was an error communicating with your AirPort card. Please make sure it is installed properly and try the AirPort Setup Assistant again.'

Obviously my card is working fine cos the extreme has no problems working, ive even been on the phone to apple who couldn't resolve the matter.

Does anyone have any idea why this is other than a faulty express??