After I had installed the Prolific Vista USB to serial driver software (PL2303_VistaDriver_Setup.exe) on my Vista Home Premium VM (installed with VMware Fusion on an iMac), I could successfully use it to read GPS track data from my Garmin Etrex H device. But after a suspend/resume or restart of my Vista VM the Prolific USB port could not be reconnected to the VM, neither automatically, nor manually through the Vitual Machine menu (USB, or Settings).
Uninstall/reinstall of the Prolific driver first helped temporarily 2 or 3 times, now it seems to be completely impossible to get it to work again.
The same driver works fine on a native (bootcamp) installation of Vista on a second iMac.