I work in networking and have the need to connect to console ports on a switch using my MacBook Pro with no serial port. I purchased the IO Gear GUC232A which works great and very well built and uses the prolific driver which has been found to be very well supported also another great more updated choice would be the pluggable usb to serial adapter

Recently with the move to OS X 10.7 (Lion) it stopped working and I found through some research that this is what needs to be done to fix it.

Here’s a way to get you PL2303-based Serial-USB adapter working with OS X Lion (10.7). Based on the osx-pl2303 project on github, utilize a kernel extension that works with OS X Lion. You can grab the kext file here or from the below attachment.

Installing the kext file can be done in a few easy steps:

1. download and extract
   
2. cd /path/to/osx-pl2303.kext
   
   
3. cp -R osx-pl2303.kext /System/Library/Extensions/
   
   
4. next you need to fix permissions and execute bits:
   
   • 
cd /System/Library/Extensions

     
   • chmod -R 755 osx-pl2303.kext
     
     
   • 
chown -R root:wheel osx-pl2303.kext
     

   
   

• cd /System/Library/Extensions
• kextload ./osx-pl2303.kext
  
• kextcache -system-cache
  
  NOTE: If you are having permission issues with any of the above commands, start them with sudo
  

osx-pl2303.kext.tgz

I signed up JUST to say...THANK YOU!....I really needed this and couldn't find a way around it.

Glad I could help