Thanks to Derik Whittaker for first documenting this.
If you're using the new partial rendering system in ASP.NET MVC and you get the following error...
CS1502: The best overloaded method match for 'System.IO.TextWriter.Write(char)' has some invalid arguments error
...then you need to change this...
<%= Html.RenderPartial("viewName") %>
...to this...
<% Html.RenderPartial("viewName"); %>
Notice: no equals sign, and an added semicolon. (Thanks to Matt Hinze in the comments for catching my typo!) The RenderPartial method returns void, as the views render directly into the output stream, not into a string.
If you want more information about why this is, check out my partial rendering blog post, especially the section titled "Implementing views: the IView interface".