Mysterious bell (ding) from Screenshot Captor

[brafoo]

Very often when I make a screen capture I will hear the Windows Ding (bell sound) a few seconds later.  The typical scenario is as follows:

1) Capture a screenshot (a selected region)
2) Add a Text caption box
3) Switch back to the program I was running originally (Screenshot Captor loses focus)
4) Some seconds later I will hear the Windows Ding sound.

This is sorta driving me crazy, so any workaround tip would be appreciated.

(Running Windows 7 Professional, 32 bit, quad-core Athlon)

[mouser]

How strange!
I can see why that would drive you crazy.
Can you try to experiment a little bit and narrow down the conditions that cause the ding sound?

[tomos]

Could there be something else trying (unsuccessfully) to use/steal the PrintScreen key?
Although I'd have thought that the 'ding' sound would happen immediately then.

The only culprit I can think of offhand is Picasa (but havent heard of it acting like this).