Emptying the Trash: not working

On Lion 10.7.3, when trying to empty the Trash from the GUI the items to be deleted are counted, and the the dialog doesn't progress anymore:

Stopping emptying the Trash doesn't help much either: the only thing changing is the status on the dialog that now reads Stopping...

It's reported that resetting the PRAM does the trick, and I know that I can just force the removal from the CLI, but can somebody help me understand why this is happening and how to fix it?

A program that is accessing files in the Trash that you're trying to Empty could interfere with attempt to Empty Trash.
The resulting timeout causes the "Stopping…" (which takes forever) alert message that you saw.

You can turn off Time Machine and try again or perhaps reboot (after turning off Time Machine) and see if the trash empties properly before starting up Time Machine or whatever other programs might have files open.

You could also try this:

1. Open Terminal from /Applications/Utilities

2. Run command: rm -rfv ~/.Trash/*

This should delete all files in the trash and show you what it's doing as it goes.