Well, first of all try taking an image without the filter - that could possibly be a factor.
Lenses wear out like anything else - and if your lens is the original one that came with the camera it could simply have worn out, or been subject to a knock. I didn't see a response from you to let us know what lens you do have, but if it's one of the earlier 18-55 kit lenses, and you attempted to manually focus it with the AF-MF set to AF, that will interfere with the focusing mechanism and definitely give you poor image quality.
The things I am getting you to test and establish or eliminate (i.e. lens issues) are the easy and cheap ones to resolve. If the body has an issue, then because of its age you are looking at a replacement - they don't fix cameras of that vintage.
So, if you want to save money or keep the camera, it's worthwhile going through these exercises to cut down the possibilities.
cheers, TREVOR
The mark of good photographer is less what they hold in their hand, it's more what they hold in their head;
"All the variety, all the charm, all the beauty of life is made up of light and shadow", Leo Tolstoy;
"Skill in photography is acquired by practice and not by purchase" Percy W. Harris
