Almost impossible to start up when anything is in the bowl. I can eventually get the ignition to "catch" but it is very intermittent and unreliable. The motor ignition is fine when using mincer.

Not locking the bowl will not in itself cause the mixer to not start. Is there more to this story you have left out?

Sounds like a worm gear problem to me, it's impossible for the motor (armature) to move far enough to not drive the gear. There are driving pins in the system from fuse gear to paddle.
1) in the fuse gear
2) inside gearbox above planetary joining shaft to bevel gear
3) through planetary and shaft

There is also one joining the little gear inside the planetary to the shaft, doubt you'd break that one though.

Tip the mixer up and look for a screw on the hinge underneath the top part. Turn this screw counterclockwise about 2 turns and the paddle will clear the bototm of the bowl.

I think you have a K45SS. It sounds like there is a problem with one of the gears, probably the worm gear. The worm gear is designed to be the first to fail if the mixer has struggled with a heavy dough or other difficult to mix substance. The best way to establish the cause will be to open the head up and check the gears for signs of damage.

There are several possible causes:1. The blades of the beater/s may be distorted (bent) 2. The beaters are in the wrong way round 3. The bottom tray is not seated down properly - there may be something in the central hole 4. The bowl may be damaged

Do you find the motor running too fast at the lowest setting? Then you need to bring it to someone to adjust the low speed setting. If you are preparing double batches you are over loading the mixer and/or using too fast a speed setting to mix. Don't try to double recipes just because the bowl can handle the volume, the motor cannot and will not last very long if stressed mixing dough frequently.

Mine is stuck too and it's so annoying. I used terry cloth and hammer the bowl to knock the bowl down (1-2 times and not too hard). I think the bowl is up a bit and over locked when doing bread dough.

Same problem here, went from working perfectly to mix cookie, now I can barely move it...help!

Don't open up the "works" part of your mixer if it is still under warranty!!!! If the policy hasn't changed, you'll void the warranty by doing that.

KitchenAid has one of the best user forums of any company as far as I'm concerned. The participants are great and the monitors are exceptional (some of the best problem solvers you are likely to run across). You may find your experience already has a thread, if not, post it. I checked in and they seem to have added a video library that has some of the topics I've seen posted at this site. Tell them "mnme" sent you. (LOL)
http://www.kitchenaidconversations.com/