I would try with regular expressions (if you don't know ii, I highly recommend to learn it, there are excellent tutorials on the web)

string test = "PascalCaseSomethingMatchAlsoASingleCharacter";
		Response.Write( test + "<br />");
		System.Text.RegularExpressions.Regex pattern = new System.Text.RegularExpressions.Regex( "[A-Z][a-z]*" );
		System.Text.RegularExpressions.Match result = pattern.Match( test );
		while( result.Success )
		{
			Response.Write( result.Value + "<br />" );
			result = result.NextMatch( );
		}

Anyway there could be problematic identifiers:

What about this:  "thisstartwithcamelcaseWhatIsNow", you can use this pattern for this for example: "([a-z]+|[A-Z][a-z]*)"

And what about his: "ThisContainsSomeIDHowToTreatThis", you can split this several ways: Some, ID, How or Some, IDH, ow [:D]