Google Reader API - feed/[FEEDURL]/ is coming back as Not found

There is one feed I'm subscribed to which always turns up as NOT FOUND when I try to use the API. I return an array of Dictionaries, containing 3 objects. The first in the list represents the user himself, like so:

{
    FeedID = "user/MY_UNIQUE_NUMBER/state/com.google/reading-list";
    Timestamp = 1273448807271463;
    Unread = 59;
}

The Unread count is very important. My client depends on downloading 59 items from Google before it refreshes. If a feed doesn't download properly, the count is off and the client won't update.

An example of a working Feed is here:

{
    FeedID = "feed/http://arstechnica.com/index.rssx";
    Timestamp = 1273447158484528;
    Unread = 13;
}

The FeedID value combines with a specially formatted URL string and gives back a list of articles. The above example works fine. However, the following feed always returns NOT FOUND on Google, and if I paste the URL verbatim into a browser, it never turns up.

See here:

{
    FeedID = "feed/http://www.peopleofwalmart.com/?feed=rss2";
    Timestamp = 1273424138183529;
    Unread = 6;
}
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http://www.google.com/reader/api/0/stream/contents/feed/http://www.peopleofwalmart.com/?feed=rss2?ot=1&r=n&xt=user/-/state/com.google/read&n=6&ck=1273449028&client=testClient

If you are at all proficient with the API, can you please help me? Like I said, since Google always says NOT FOUND when I search for that feed, my download count is off by N articles and won't update. I would rather not hack around it, honestly.

Thanks!

The URL string wasn't escaped properly, and the "?" in the middle of the base feed URL confuses Google Reader. I had to escape the string which turned the ? to %3F.