Need help with odd behavior for checkbox (I'm using version 2.2beta)

I put two checkboxes on a form and they both have different behavior. One checkbox has the normal state, either checked (with arrow) or unchecked or unchecked. The other checkbox has three states. Checked, unchecked, or turned into a square box that seems like it's checked. Here's something I'm not understanding. If I delete the checkbox that has three states, and do a copy & paste with the one that works right, the checkbox has only 2 states. The only way I know that you might be able to reproduce this is to just start adding checkboxes on a form and see if it happens.

If someone understands this, or knows of a workaround, let me know

thanks