When attempting to try and access the url of the sites or the SSP admin site from the local server I kept receiving logon prompts even though I was logging on with the farm account. Interestingly I could logon to the SSP and sites from other servers / client pc’s with no problems.
I initially thought someone had changed the content access (crawl) account so reset this but to no avail.
After some further investigation noticed in the security event log that I was receiving access denied.
Modifying the registry using method 2 from the article below fixed this issue: