Problem with rate limit on API

Hi!
I`m using twhirl for twitter and it regularly returns an error "Rate limit exceeded, retry in 5 min". It does this even if it is first time a day.
I`ve visited the page http://twitter.com/account/rate_limit... and it returns me the following
−
<hash>
<remaining-hits type="integer">-456</remaining-hits>
<hourly-limit type="integer">20</hourly-limit>
<reset-time type="datetime">2008-07-01T07:24:26+00:00</reset-time>
<reset-time-in-seconds type="integer">1214897066</reset-time-in-seconds>
</hash>

I`ve waited 10 min and refresh the page
−
<hash>
<remaining-hits type="integer">-608</remaining-hits>
<hourly-limit type="integer">20</hourly-limit>
<reset-time type="datetime">2008-07-01T07:24:26+00:00</reset-time>
<reset-time-in-seconds type="integer">1214897066</reset-time-in-seconds>
</hash>
Actually, I didn`t make any hits at all.
It seems like something is wrong with API functions.