kaled - 8:10 pm on Jul 16, 2003 (gmt 0) Welcome to the Google Rollercoaster. Kaled. PS
Transition periods are frequent on Google. During these periods results are not consistent. If yours is a new site it will probably settle at or around the higher positions. However, this could take anything up to three months.
There has been speculation over the last few weeks that Google is moving to a rolling update from a monthly (ish) 'dance'. You should check out threads on this subject.
Welcome to the Google Rollercoaster.