Checking Google's cache gives error.

We're sorry... but your query looks similar to automated requests from a computer virus or spyware application. To protect our users, we can't process your request right now.

We don't run automated queries from our dedicated IP. All computers are spyware / virus free. I'm using the Google toolbar for this query. This happens when I try to check the cache on any site. I've checked maybe 3 or 4 cached pages this hour, could that be the problem? If so, that seems pretty sensitive.