I think that BU353 uses a prolific chip to convert serial
data into USB data.
If you have other prolific adapters in use, that might conflict with the GPS.
In windows7 you can still get access to the control panel
and connected hardware
See if your GPS sensor it still there, and if it has the same com port number.
You could also visit prolific's website and download a more recent (and hopefully more reliable) driver for your windows version.
Be sure to always plug
in your USB plug
in the same USB socket on your system.
If you do not do that, windows (and / or or the driver) will see it as a new device and will assign a new com port number to it.
If you use an USB hub, that is the same as using an other connector in your system, so always use the same connector on that hub too.