Okay. I'm having some sort of a problem with my D40 lately. After 29,000 shots (give or take a few hundred), my shutter button is getting harder and harder to press and sometimes when I do press hard enough, it takes two consecutive shots (I shoot in Single Shot mode but it behaved like a Continuous Shooting). The consecutive shooting is rare but it's just getting harder and harder to press. So my question is... does it mean that my shutter mechanism is coming to an end of its life or it's something else.
I am not familiar with the D40 but perhaps the shutter selector has got dislodged to half way between single and continuous shooting. If you turn the body upside down, gently tap the base and use a soft brush to get under the shutter release button you might get lucky and dislodge any debris.
Photography is a bit like archery. A technically better camera, lens or arrow may not hit the target as often as it could if the photographer or archer does not practice enough.
I couldn't take it anymore, the shutter release button was giving me problems so much that I just had to send it in to Nikon. Two days later, Nikon calls me up and told me that they need to replace the "Release Switch FPC" (whatever that is), and total cost would be 60 USD. I said, "Fine, go ahead".
Next day, I got another call to ask me to pick it up.
When I got there, I was told that they replaced the switch, upgraded my firmware (mine was 1.11) and cleaned my sensor. I'm happy again.