My version of Microsoft Windows Vista comes with a screen capture tool called the Snipping Tool. It is a very useful tool which I often use. With this tool you can capture a screen shot (snip) of any part of your screen and save it to the clipboard or to a file in a number of formats (HTML, PNG, GIF, or JPEG). Available snip types include free-form, rectangular, window or full-screen.
One day last week the Snipping Tool suddenly stopped allowing me to save a snip to a file. No error messages or message of any kind. Pressing the Save option simply did not nothing. The warning message about saving a unsaved snip still appeared when exiting the Snipping Tool but did not allow me to save the snip.
After some research I stumbled across the answer. It turns out that I had deleted the Pictures folder in my user folder as part of a cleanup of my folders. I never use that folder so I naively assumed that I could delete it.  However if you delete that folder, the Snipping Tool does not display a Save File dialog box. Note that the Snipping Tool does not force you to save a snip in your Pictures folder but does require you to have the folder! You can save the snip anywhere you like provided you have the right permissions.
What a poor user interface design! As part of Vista QA did nobody test this scenario? If it was a deliberate design decision to require the Pictures folder, why not display a dialog box warning the user that the folder is missing and is required?