The only other way I can reproduce that is when there is no selection. You do get those 'crawling ants` marking the selection after using the fuzzy / color sectect tool? Are they visible?
An alternative to the delete key is ctrl-x
Can you post a screenshot of the whole Gimp interface, tools, image, layers
An alternative to the delete key is ctrl-x
Can you post a screenshot of the whole Gimp interface, tools, image, layers