I know this is very annoying. An Error pops up when I need to finish an urgent design on Illustrator. Yes it’s the same that you may come across too. I reinstalled Illustrator CS4 again. It just used to waste my time. I have seen this error comes on Illustrator CS2, CS3 too. Unfortunately no one answers the question properly. Nevertheless this is how I figured it out.
According to my experience, this error comes If your computer restarts suddenly while Illustrator is being opened.
“Missing required plugin pathfinder suite” is the error. There are more errors similar to “Missing required plugin BRS pencil tool ExpandS Pathfinder Suite ”
To solve this problem let Illustrator create a new preferences file. If the error is still on the screen, click OK to quit the error and go to
Documents and Settings/user profile/Application Data/Adobe/
(By default “Application Data” folder is hidden. Therefore to show this particular folder, go to Control Panel –> Folder Options –> Click on View Tab –> Remove the tick from “Show hidden files and folders then click on OK and Apply.)
You can see there is a folder called “Adobe Illustrator CS4 Settings” rename this folder to “AIPrefs_old”
Right! you are done. Without hesitation open the Illustrator now. I assure you that it won’t give you the error again.