What happened to zero

[m2tts]

I have a bip file where I have rotated the model to take a shot of the bottom, as if the product was lifted from one side. The file was saved after an unsucessful render (but that is another story). Now today I open the file again and want to rotate it completely upside down; but when I go to enter numbers into the rotation boxes I get some very strange results. I cannot get the model back to zero. Zeros go in and the model rotates to something arbitrary. You click on the model and the rotation boxes are filled with random rotations. No matter how many times you enter numbers, you get unpredictable results. Heisenberg was right.