File already open (Error 55)
Sometimes a file must be closed before another Open or other operation can occur. This error has the following causes and solutions:
A sequential-output mode Open statement was executed for a file that is already open. You must close a file opened for one type of sequential access before opening it for another. For example, you must close a file opened for Input before opening it for Output.
A statement, for example, Kill, SetAttr, or Name, refers to an open file. Close the file before executing the statement.
For additional information, select the item in question and press F1 (in Windows) or HELP (on the Macintosh).