I have a new single fixture file from the library dept, I am trying to merge it into my current show v 4.0.96, the new fixture is v 4.2.155, I have tried several times to merge and get all the way to merge finished with "Merge Failed" on the line before.
It's possible your show is full. Try stripping the unused types from your show file first and then doing the merge. To strip unused types hold Pig+Open+5, and select the Strip Unused option from the toolbar that is on the top of your right hand screen. Then log off/on and try the merge again.