The nice thing about SMF2 is that you can find out EXACTLY which edit failed. Just find the place to click on the line that failed, and you will see exactly what the Package Manager was looking for, and exactly what it was hoping to replace it with.
What has happened is that one of your other mods changed that part of the file, so the package manager cannot find the text it is looking for.
But you are smarter than package manager. You can find the right part of the file, and make the required change.
Here's what to do:
1) Make careful note of the part that failed. Figure out exactly what needs to be changed, and how you will change it
2) Do the install, using Package Manager.
3) Go back and make the manual change you figured out in step 1.
If you have done this properly, everything will work.
If you ever decide to uninstall SimplePortal, you will have to undo this part of the install manually, also.
Please see the SimplePortal documentation for more information:
http://simpleportal.net/index.php?action=docs;area=solving_install_problems