Very easy to reproduce:

Type into your browser www.google.com/ig and you get iGoogle nothing strange there.

igoogle

Type in www.google.com/IG and you get a 404 error?? Really what happened to my iGoogle homepage?

404

Surely the good people at Google follow HTTP Protocol standards http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html namely:

3.2.3 URI Comparison

When comparing two URIs to decide if they match or not, a client SHOULD use a case-sensitive octet-by-octet comparison of the entire URIs, with these exceptions:
      - A port that is empty or not given is equivalent to the default port for that URI-reference;
        - Comparisons of host names MUST be case-insensitive;
        - Comparisons of scheme names MUST be case-insensitive;
        - An empty abs_path is equivalent to an abs_path of "/".
Characters other than those in the "reserved" and "unsafe" sets (see RFC 2396 [42]) are equivalent to their ""%" HEX HEX" encoding.

For example, the following three URIs are equivalent:

      http://abc.com:80/~smith/home.html http://ABC.com/%7Esmith/home.html http://ABC.com:/%7esmith/home.html

I've posted a question on the iGoogle forum, I will let you know what response I get and whether the response (like the request) is case sensitive :-)