I have a singer hd110, the bobbin case broke and was replaced. Ever since then the upper thread gets stuck and breaks down in bobbin. I have reinserted more times than I can count!

SOURCE: Singer 5817C bobbin pulls out of casing

This will happen if the bobbin is put in the wrong way around - I believe the thread should be going in a clockwise direction as you face it. (If this is the way you have it, try the other way!)

SOURCE: Singer 6233 - broken bobbin case

You can order one online, I am not sure about shipping costs.
http://www.vacsew.com/vacuum/singer-apollo-bobbin-case.html?printable=Y
I jsut bought one for $15 at my local sewing store.

SOURCE: Not picking up the Bobbin thread

I cleaned the machine good with canned air, oiled it. I took out the bobbin case and cleaned it good also. I then noticed the tension screw on the bobbin case was loose, tightened it and the problem was fixed.

SOURCE: bobbin case and threading singer 6423

This machine has a black plastic bobbin case. You drop the bobbin down into the case with the thread coming off in a clockwise direction. If you look close you will see a slot in the bobbin case where there is the metal pieces. The thread will slide into that and as you pull on it it will work its way through and come out on the other end of the metal. Lay the thread over top of the bobbin case and turn the handwheel to pick up the thread. (make sure you close the slide plate)

SOURCE: Singer Sewing Machine model 9224. Bobbin thread

If you turn the handwheel, can you see a metal ring rotating around the outer edge of the bobbin case? If not rotating, broken gear or timing belt off.
If that ring is turning, remove the needle plate and bobbin case. As this ring now rotates, you will a finger on the ring that will pass behind the needle from right to left and it should catch the thread from the eye of the needle. If this finger, the "hook" passes above the eye, you have a timing problem.

Let me know.