When I try to paste-link data from Excel, the command is not available (gray).

We know of four reasons for this.

• You can only paste link data from a saved Excel file. If you just created an Excel file, it won't have a name, so you can't link to it. Save it first.
• If you are logged in without admin rights, try running Prism once with admin rights. This will reset some registry entries which might fix the problem.
• Prism 4.00 will only show the Paste Link command when the total length of the path ("C:\this\that\somewhere\filename.xls") is less than 78 characters. Shorten your folder or file names, or use less nesting, and Paste Linking will work fine. Fixed in 4.01. 
• Prism 4.00 also can have trouble with paste linking from an Excel file saved on a shared network drive. Move the file to your local hard drive, and paste linking will work fine. Fixed in 4.01.