A project's procedure, variable, constant, and parameter names are stored in a name table. This error has the following cause and solution:
The name table may contain some temporary duplicates. You can compact the name table by saving the project to a disk, and then closing it. If the problem persists after you reopen the project, reduce the number of names by reusing local variable names in multiple procedures, and then recompact the table by saving the project, closing it, and reopening it.
For additional information, select the item in question and press F1 (in Windows) or HELP (on the Macintosh).