"Save" and "Save As" dialog box does not appear.

[gdv]

Can't "Save" or "Save As" from "File" menu. The dialog box
simply does not appear.

 

[Murthy]

Check for viruses with latest AV definitions.

 

[Dave Peterson]

Just a little more info:

There was a virus that affected the File|Save, File|SaveAs and File|Open.

http://support.microsoft.com/?kbid=308360
OFF2000: Error Messages Caused by Nimda Virus When You Open or Save
Files in Office Programs

maybe you got hit.

If this isn't it, do you get error messages?

===
And you may want to try resetting that option on the toolbar.

Tools|Customize (just to see that dialog)
click on File
rightclick on SaveAs
select Reset

Test it out.