Thanks for posting with your issue, I’ll be happy to help!
The 1.5 driver is the latest greatest version, newer than the older 1.4 version. Is there some reason you’re trying to use the older version?
Also, just for public record, our install walkthrough for USB Serial on OS X is at the link below if you’d like to work ahead: http://plugable.com/2011/07/12/instal…
Let’s first verify which kernel extension/driver you’ve got loaded so we can make sure the driver install actually worked by doing:
kextstat | grep prolific
My system returns:
127 0 0xffffff7f81fd4000 0x8000 0x8000 com.prolific.driver.PL2303 (2.0.0)
Note that version 2.0.0 is reported even though I’ve installed 1.5. Please let me know what you find for the command above and the additional detail will help recommend our next steps.
If we find the above driver is loaded, we’ll move on to checking USB serial device enumeration using:
ioreg -c IOSerialBSDClient | grep usb