Sometimes I get a bug with GUI. Focus received another field.

This is the second time I got the so bug http://www.youtube.com/watch?v=oZUanimRg_w&feature=youtu.be When I click on FloatField or TextField, the focus received another field. This bug is happened suddenly only for my editor script. I have tried to delete all of the code from the script, opened other projects, but it did not help. But soon the bug itself has disappeared.