If you are downloading the new driver from the Internet, make sure to select “Save” from within your Web Browser and not “Run”!
Use the latest version of Stuff It Expander by Aladdin Systems. Within StuffIt Expander, make sure that Convert text files to Macintosh format is set to "Never". Then click OK. Otherwise, the driver files might be displayed as text files. Also, compare the original file name that is displayed on the download page with the file name of the downloaded file. If they differ, rename the downloaded file to the name you see on the download page. Sometimes, web browsers truncate some letters at the end of the file name (often the correct file extensions) and this causes the computer not to recognize the file.

If the extraction of the downloaded file was successful but your Mac fails to open an ".mpkg" or "*.pkg" file, make sure your Mac is configured to open such files with the "Installer" program. You can check this by Ctrl-clicking on the mpgk/pkg file and selecting "Open With". If the first choice in the list is not "Installer (default)", then you will need to change this. In this case, select "Other..." from the same menu, in the "Enable" field, select "All Applications" and then browse to the Installer program, which is located in Applications/Utilities. Activate the "Always Open With" checkbox and then click "Open".