Recently an adobe forum member, that goes by the name hans blix, posted about a problem with deleting files that were manipulated with CF's image functions, under CF 8.0.1. The image files seemed to be locked and could not be deleted until ColdFusion was restarted.
In his case he was reading an image with <cfimage>, resizing it, then deleting the original file. Apparently, ImageResize() seemed to be locking the image file. So the call to delete the original image generated an exception:
ColdFusion could not delete the file <path to image file> for an unknown reason.
Fortunately, Ken Smith mentioned there is a patch for this issue. So if you are also encountering this problem, you can find the patch here: Patch for CFImage and Image functions in ColdFusion 8.0.1 (kb403411).
UPDATE: The image hotfix was updated on 08/15/2008. The file name is exactly the same as the one released on 05/07/2008. So check the file timestamp to make sure you have the latest fix.