Hi Brenda,
I am not able to reproduce this problem, relinking files behaves the same for me in 4.2 as 4.1. Also, this:
"Each time I switch over I have to relocate my program to my photos - which is expected."
is actually _not_ expected. If you have your photos and catalog together on an external drive, and you move that drive between computers, Lightroom should not lose track of the photos, as long as the photos are together on the same drive with the catalog.
I have a few questions for you which might help us track down the problem, but first I have a suggestion which might help you work around your current difficulty.
I assume that when you move to another computer, the thumbnails of your images have a little question mark icon in the upper right corner, like this:
When you attempt to relink your photos, are you doing it by clicking on that question mark icon? If so, here's something else to try. Is the Folders panel also indicating that the folders are missing? Missing folders all have question marks on the folder icon, like this:
If your folders have question mark icons like that, then try this: right-click on the top-most folder ("04" in the case of my example) and choose "Find Missing Folders". Then locate the folder, and click OK. That should find that folder, and all the folders that it contains, and all of the photos that are in any of those folders. Let me know if that works for you.
Here are some questions you can answer that will help us figure out the problem.
1. What Mac operating system version are you using?
2. What Windows operating system version are you using?
3. Where was the Lightroom catalog created? (In other words, was it created on the Mac originally, then opened on Windows, or the other way around?)
4. How old is the catalog? (In other words, what version of Lightroom was the catalog originally created in?)
5. What sort of external drive are you using? (A regular USB drive, or something else?)
Thanks,
Ben