I shut down my MacBook Pro and disconnected my second monitor. Then I started my MacBook Pro and opened Lightroom 4.3. It worked great. No problems switching modules. However, when I reconnected the second monitor and tried to go to the slideshow module the message, an error occurred when attempting to change modules, was displayed again. I still get the error message with the second monitor set on loupe, grid, etc. With the second monitor unplugged everything is fine. With the second monitor plugged in, the problem reoccurs.

I called Adobe and let them fiddle online with Lightroom on my MacBook Pro. The Adobe tech claims I have a corrupt permissions file. He told me to contact Apple and have them rebuild my permissions file.

When I contacted Apple, the tech said to startup my MackBook Pro with the option key held down until the first screen appears. Then click on: Recovery HD, arrow, Language, Disk Utility, Macintosh HD, Repair Disk Permissions.

I did this three times, but some permissions were not repaired. Another Apple tech then suggested I bring my MackBook Pro to a Macintosh authorized repair shop, and have them repair my permissions file. I asked if I can buy Norton Utilities or a similar program and do it myself. The Apple tech said yes, but an authorized repair person will know which permissions to repair and which ones not to touch.

Unless someone on this forum can tell me how to do this repair myself, I’ll get it repaired next week. And, I’ll post the results as soon as I can.

How do I remove Lightroom 4.3 without removing Lightroom 4? Do I just delete the Lightroom 4 icon in my MacBook Pro's applications folder? What about preference files and permissions? If I delete Lightroom 4.3 and install the Lightroom 4.2 update, will the photos I edited in Lightroom 4.3 retain their edits?

In my last post I mentioned that I called Adobe and allowed their technician to take control of my MacBook Pro to solve this problem. After doing diagnostics on my MacBook Pro he claimed the problem was due to a corrupted permissions file, and suggested I talk to an Apple technician. So, I called Apple and their technician said the Adobe technician was probably right, and referred me to an Apple authorized repair shop - the only one around where I live. The technician there said he could fix it, but he had to keep it longer than I could go without it. I use it every day for work. If someone from Adobe could give us a rough estimate of how long it will probably take to release an update with a fix for the problem, I might just live with the inconvenience until then.

Once again, thank you for your help.