When does natural keyword use become excessive?

[vero]

I have a fairly lengthy page on a topic, that gets lots of traffic from msn and yahoo, and none, nada, zip from Google. It's indexed by Google, there are external links to it, but for months it has received no Google traffic. (My other pages do fine)
I did a count. There are approx 1500 words, all about widgets. In the course of writing, there's talk of red widgets, blue widgets, etc, so the total number of times "widgets" appears is 78.
Is that too high a percentage? Does it look like keyword spamming, even though it was just the natural way to write the sentences?

[tedster]

Google's algo goes far beyond a mere count of keywords, or even a percentage. It may not even be the specific keywords themseoves, but semantically related phrases, or how the keywords are used on the page, that is causing the Google ranking problem for you.

For more information, you can check out some Google patents that we discussed in this thread:

Phrase Based Indexing and Retrieval [webmasterworld.com]

[Robert Charlton]

I've been wondering how Google might take an article's audience into account, as that might significantly change the frequency of certain vocabulary.

An article directed toward an in-group might rarely mention the subject phrase, because it would be implicit in the discussion, and might use a lot of technical vocabulary... whereas an introductory article might mention the subject phrase a lot, and might go light on technical vocabulary.