anyone have this problem? it has a small knob that tightens it to the hot shoe, but it keeps loosening and falling off. any solutions/hot shoe locks??

I've had quite a few of the "cheap" models precariously leave my monitor dangling. Especially with the big batteries. It's scary. The ones that we use now are a model made by Manfrotto. The model is the 492 DVeStore - Search Results for "492" (http://www.dvestore.com/search.php?search_query=492&x=0&y=0) These tighten nicely.

You may also want to consider a Noga arm if your monitor has a top thread. I've found that mounting from the top seems to distribute the weight easier when run-n-gunnin'. IKAN has some inexpensive arms http://ikancorp.com/productInfo.php?id=58, and Zacuto has some really nice ones, although a bit more. http://www.zacuto.com/