When you place a PSD or open a file that contains a link to a PSD, Illustrator returns the following error:
"The file is not readable."
The PSD has spot channel defined with a color book that is not installed in your instance of Illustrator.
Work with the file creator to determine which color books were used in the definition of spot channels. Then, install those color books on your system. Alternatively, the file creator can edit the image as described below, using a color book that you both have in common.
Open the Channels panel and double-click the Spot channel.
Click the color in the Spot Channel Options dialog box.
Click OK twice to exit the Spot Channel Options dialog box.
If you want to be sure that others can open your Illustrator file regardless of which color books they have installed, embed the image rather than maintain a link to it. Place the image again and choose deselect the Link option, or use the following method:
From the Links panel pop-up menu, choose Embed Image.
One of the most common causes of this issue is the use of the new PANTONE® PLUS Digital Libraries for Adobe® CS. Make sure that when you define spot channels with these libraries that other users who work with the files also install them. For more information, see PANTONE® PLUS Digital Libraries available.