Ever since we set up a test SharePoint 2010 server my copies of Office 2010 would prompt me for credentials to the test farm (even if I didn’t have anything open from that farm).
It would happen in every office application and usually a couple or three times a day (which if you have Excel, Word, Visio, Project, and Power Point open adds up to a lot of credential challenges.
Since this site was not part of my corporate domain, the normal solution (trusted site, auto pass along credentials) was not the correct fix, so I kept digging. Search engines failed to find anything on the topic (except for a lone MSDN forum where another person had the same problem).
I wondered if it had to do with the Office feature where it will ask to remember your MySite for you…so I did a registry search for the host name of the SharePoint farm, and I found this interesting key
It seems that in Software\AppDataLow\ there is a hive for Office 2010 that stores a key called PersonalSiteUrl along with a LinkPublishingTimestamp. In the PersonalSiteUrl key was the URL of my MySite on the test farm.
I deleted the key value and navigated to the MySite on the test farm and it asked me if I wanted Office to remember my MySite and I told it no. The problem seems to have gone away.