Kathleen,
Assuming you have AC3 boards, the white/blue LED is normal (White to indicate connection and blue to indicate a pen is detected).
If you have no light, this could mean one of a few things depending on your model of board and how you're connected to power; however I can safely generalize to say that it will either mean that you're getting no power, your board is not being detected correctly by the computer via USB, or both.
I'd like to know whether your board has an amplifier on the left and if so whether this is powered on (ie whether the On/Standby button is red, green or off, if red please press it to power up).
Next I'd ask whether the USB connection at the back of the board and to the computer is secure, and whether the computer has drivers installed. Given this is happening with two computers at the same time, I'd want to confirm whether there have been any updates pushed out recently. I'd also want to try connecting the board to a different USB port.
Lastly, I'd want to know whether there are any intermediate connections in your USB connection, and whether these are secure. It may be worthwhile to bypass and connect directly from the board to the computer using a single 16' length of USB cable.
If none of this helps, please collect your board's serial number and contact us via email through your knowledgebase (www.prometheankb.com) or using the phone numbers at prometheanworld.com. I've logged this post against case 253889, please reference this when contacting us.
Thank you,