Assuming you are using Windows, even though you said you "went through all the driver stuff", you might want to consider booting in SAFE mode, and deleting all the instances of the USB root hub and associated devices. This will force Windows to reload them on a reboot. It's possible there is a device conflict that it just hasn't figured-out. Also, you may want to check under Hardware Profiles and see if more than one profile exists for the system. Given it's a laptop, it may have created an alternate "docked" configuration and disabled the device in that, or the default configuration. If so, delete the alternate hardware profile and let it rebuild.
Be certain that the device itself isn't marked as disabled in the profile. Given what you said in your question, it sounds like the device isn't even showing-up at all in the Device Manager? Not even as an Unknown Device?
If you insert it into the USB port and there is no audible beep to indicate that Windows knows it was inserted (or likewise if you remove it) , you likely have a hardware problem. Even if you say for certain that the USB ports are working, it is possible that the driver and/or the hardware is failing and it's only operating as a USB 1.x device, which could make the NIC not function (especially if it is USB 2.x compliant).
Since you can take the USB card to another system and say it works fine, that would appear the problem is related to your laptop.
You also might want to check the power management capabilities to ensure it is not powering down the network card and/or USB hubs to conserve power. Even if the unit is plugged-in, if for some reason it is running a power-saving scheme, you might have this problem.
if you can provide the specific version of Windows and Service Pack (or Build Number), that would be helpful. if you are not running windows (e.g. Linux) please provide that info as well (include the distribution, release, update number and kernel from uname -a).
Good Luck!