wakes every night

[moonbeam]

I have a 12 yr old with ADHA, a 7 yr old with cp sz, a 3yr old who sleeps with eyes partially open, and a 5 yr old who wakes every night. She is the reason for this post. Every night, usually the same time period, she begins to cry and then awakens. She is only ever awake long enough to get a kiss and a hug from mommy and then she's back off to bed. She will then immediately return to sleep and sleep all night. Does anyone have any suggestions as to what may be causing this? I monitor what she eats, drinks, watches on tv, etc. I haven't found a link.