I have never taken Lamatical, however, vivid dreams are very much a part of life for me. I find the dreams are so real to me that I am haunted for days, trying to figure out what is real. In one istance I dreamt that my brother was killed, it took me three days to not be startled to see him walk into the room.
I would suggest charting (however you wish to) your moods and then the dreams you have. I found that mine are very much related to stress and depression, and I rarely get them when I am hypomanic. I know it doesnt help take them away, but it may give you some answers, which in itself helped me not be so freaked out at my in-ability to separate dreams from reality.
Hope this helps you out. Good Luck.