I recently received this "Ambiguous match found" error in an app I had recently converted from visual studio 2003 to visual studio 2005. The error was particularly unhelpful in letting me know what the problem was. So, like always, I turned to Google in the hopes that someone else had had this issue. I found the page, linked to above, where I got this quote. I was particularly impressed had how similar this guys issue was. I am guessing that this error only plagues converted c# apps.
[quote] Other Google search results were similarly unhelpful, until I found the blog of a guy named Eran Sandler who talked about his "Ambiguous match found" error and how he solved it--two protected fields with names that differed only in case, apparently confusing reflection. [/quote]