Make sure you have installed the 64 bit version of the Keyspan drivers because if you installed the 32 bit drivers, they will install correctly but will not run if your system started in 64 bit.
If you want to use the older version of the drivers (for whatever reason), you will need to make sure that your Mac starts in 32 bit mode.
To know if your system has started in 64bit or 32bit, you can start System Profiler by going to the "About This Mac" menu and then click on "More info...". If you then click on "Software in the left column, you should see a line that tells you:
- 64-bit Kernel and Extensions: No = means your system is in 32bit and you should have no issue with the Keyspan drivers
- 64-bit Kernel and Extensions: Yes = means your system is in 64bit and the Keyspan drivers will not work
To force your computer to start in 32bit, there are different solutions that you can find on the internet. One of them is to hold the 3 and 2 keys pressed while starting the computer to force to start in 32bit. (Or hold 6 and 4 for 64bit).
Also attached you will find an application (K64Enabler) that can do that (at your own risk) if required.
!!! Be aware that we are providing this information as is and can not be liable to any consequence these manipulations may have. You should also know that when starting a Mac OSX Server in 32 bit all the Mac OSX Server services will be working in 32bit and can then be slower. You will do this at your own risk, and we strongly recommend that you search for information on the internet before proceeding.