down loaded lightroom 5 and installed but won't open right. On opening Message "an error occurred when attempting to change modules"

Have a Mac Book Air with Lightroom 4 Full Download aboard. Just got an iMac. Wanted to load Lightroom 4 on iMac. Took the Adobe download file off the Mac Air and tried to load it on the iMac. It was successfull but on opening  the message "an error occurred when attempting to change modules" appeared. I removed Lightroom 4 and went to Adobe orders and re-downloaded my original order to the iMac. Same effect. Bought full Lightroom 5 hoping to fix but the same message appeared. What's up! Any help?