Whilst porting an ASP.Net application to the .Net 2.0 framework, I came across a spurious error when viewing a few specific pages. The error was occurring during the runtime compilation of these specific aspx pages.
Parser Error Description: An error occurred during the parsing of a resource required to service this request. Please review the following specific parse error details and modify your source file appropriately. Parser Error Message: Ambiguous match found.
To make this error more confusing, the error was reported on line 1 of the aspx page which contained nothing more than the page directive tag.
After a bit of searching, I found the cause of the problem. The cause was that there were two member variables declared with names that differed only by case (one was an ASP.Net PlaceHolder control, the other an int). Simply renaming one of the variables solved the compilation error.
Eran Sandler has also encountered this problem, but delves a lot deeper into what is going on.