How to solve the error "The command cannot be performed because a dialog box is opened" when you try to open a file in Word 2007 or 2003?

When you try to open a file in Microsoft Office Word 2007 or in Microsoft Office Word 2003, the file does not open, and you receive an error message as follows:
The command cannot be performed because a dialog box is opened, click OK then close open dialog boxes to continue.

There are 2 options to fix the error.

Option 1:
This problem may occur if the Officeav.dll file is corrupted or outdated. The Officeav.dll file is the Norton AntiVirus Office plug-in.
To resolve this problem, rename the Officeav.dll file. To do this, follow these steps.

1. Click Start, click Search, and then click All files and folders.
2. In the All or part of the file name box, type officeav.dll.
3. In the Look in box, click Local Hard Drives.
4. Click Search. When the search result is displayed in the right pane, note the path of the Officeav.dll file.
5. Locate the Officeav.dll file, right-click officeav.dll, and then click Rename.
6. Type officeav.old, and then press ENTER.
7. Restart your computer.

Option 2:
This problem may occur if you have a Word template in your Startup folder that contains an autoexec macro that opens a dialog box.

To remove a template from your startup folder, follow these steps.
1. Exit Word 2007 or Word 2003.
2. Click Start, point to Programs, point to Accessories, and then click Windows Explorer.
3. Locate one of the following folders depending on which operating system you have installed:
C:\Documents and Settings\username\Application Data\Microsoft\Word\STARTUP or
C:\Users\username\AppData\Roaming\Microsoft\Word\STARTUP or
C:\Program Files\Microsoft Office\OFFICE12\STARTUP
4. Double-click the Startup folder to open it.
5. In the right Windows Explorer pane, click to select the template that you want to remove, and then press the DELETE key.

Note that because there are several versions of Microsoft Windows, the steps may be different on your computer.