Window Problems

I purchased a newly "redone" or "flipped" house in late 2009 and some windows have have developed problems. First within the first year one side of a small window in a bathroom cracked and a friend said it was evidently from "stress" and that the window probably wasn't installed properly.

If I replace the pane that cracked would it likely crack again?

Then a bedroom east facing window started making "popping" sounds this past year in the morning when the sun started to hit it and I discovered that it seem to have "moved" within the frame .in other words it seems to be "falling out". I see cracks in the paint and possibly caulk around it on the inside and you can push on the window and tell it is loose because it will move slightly.

I was told by a friend that they probably used the wrong type of caulking when the windows were installed and that it didn't allow for expansion and contraction. This friend also said I could just re-caulk over the existing with New Proper Type Caulk. Is that true? Or what is the proper way to fix this before it starts to leak? I feel I should have All windows fixed before they start to do the same.

Also, What type of Contractor would I contact for these repairs? A general contractor, a window installer, etc???

Thank you.

Mary