Hi Brad,The 503 error usually means Google has banned your IP for too much use.
Google is getting much tighter with any query that looks like it may be fore SEO research.
I don't have the ability to use proxies built into Tuelz, so you will either need to wait until the ban is up, it could be from 4-24 hours, or change IP addresses. If you are doing serious research, you may want to use some type of proxy rotator like www.HideMyAss.com or find and change your proxies by hand in IE.