well I've created something in Expression Blend and both the XAML and javascript work fine, but then I add it dynamically using .net and I get an error with saying basically that it can't begin() the storyboard. Here is what the dynamic XAML looks like:

StringBuilder sb = new StringBuilder();

            sb.Append(@"<Storyboard x:Name=""SB" + xamlObjectName + @"_Enter"">
			                <DoubleAnimationUsingKeyFrames BeginTime=""00:00:00"" Storyboard.TargetName=""" + xamlObjectName + @"_SubRect"" Storyboard.TargetProperty=""(FrameworkElement.Height)"">
				                <SplineDoubleKeyFrame KeyTime=""00:00:00"" Value=""22""/>
				                <SplineDoubleKeyFrame KeyTime=""00:00:00.2000000"" Value=""30""/>
			                </DoubleAnimationUsingKeyFrames>
			                <DoubleAnimationUsingKeyFrames BeginTime=""00:00:00"" Storyboard.TargetName=""" + xamlObjectName + @"_SubRect"" Storyboard.TargetProperty=""(UIElement.RenderTransform).(TransformGroup.Children)[3].(TranslateTransform.Y)"">
				                <SplineDoubleKeyFrame KeyTime=""00:00:00"" Value=""0""/>
				                <SplineDoubleKeyFrame KeyTime=""00:00:00.2000000"" Value=""-8""/>
			                </DoubleAnimationUsingKeyFrames>
		                </Storyboard>
		                <Storyboard x:Name=""SB" + xamlObjectName + @"_Leave"">
			                <DoubleAnimationUsingKeyFrames BeginTime=""00:00:00"" Storyboard.TargetName=""" + xamlObjectName + @"_SubRect"" Storyboard.TargetProperty=""(FrameworkElement.Height)"">
				                <SplineDoubleKeyFrame KeyTime=""00:00:00"" Value=""30""/>
				                <SplineDoubleKeyFrame KeyTime=""00:00:00.2000000"" Value=""22""/>
			                </DoubleAnimationUsingKeyFrames>
			                <DoubleAnimationUsingKeyFrames BeginTime=""00:00:00"" Storyboard.TargetName=""" + xamlObjectName + @"_SubRect"" Storyboard.TargetProperty=""(UIElement.RenderTransform).(TransformGroup.Children)[3].(TranslateTransform.Y)"">
				                <SplineDoubleKeyFrame KeyTime=""00:00:00"" Value=""-8""/>
				                <SplineDoubleKeyFrame KeyTime=""00:00:00.2000000"" Value=""0""/>
			                </DoubleAnimationUsingKeyFrames>
		                </Storyboard>");

Each storyboard has 2 DoubleAnimationUsingKeyFrames, it seems that if I remove 1 DoubleAnimationUsingKeyFrames from each storyboard everything works fine. Yet the same thing works fine when I do it with Blend. Anyone have any idea why this would be happening.

If the code you produce with FrontPage worsk and .NET doesn't, my first guess woudl be malformed XML. Try using the XmlDocument class instead of a string builder?