Error in for loop

I have this for loop:

for (var i in jsMonsters) {
*<p>Which gives me this error message:</p>*
 *<p>InvalidCastException: Cannot cast from*
 *source type to destination type.</p>*
*<p>Can you explain why that is happening?</p>*
*<p>Thanks - Elliot Bonneville</p>*
*<p>Also, so I don't have to edit my Question with more information later, here's what populates the array:</p>*
*function ReadFile () {*
 *var sr = new StreamReader(Application.dataPath + "/" + readFilePath);*
 *var fileContents = sr.ReadToEnd();*
 *var monsters : String[] = fileContents.Split("-"[0]);*
 *var jsMonsters = new Array(monsters);*

It should just be Debug.Log(i);

It's already the string you're interested in