I don't know why, but some days you wake up and things have just changed overnight. You may find yourself in love with a co-worker or realize you really like jelly donuts for the first time.
For me a change happened one morning when the "Find and Replace" panel in Visual Studio 2010 started disappearing after its first use. Very annoying. After a while, really, really annoying. The fix in my case was to open "Tools/Options/Environment/Find and Replace" and uncheck "Hide Find and Replace Window...". I don't know how it got set in the first place, but some mornings you wake up and things are just different - now where is my jelly donut?