Linked Server errors, such as between SQL Server 2000 and 2005 versions are quite common in DBA-day life. When it goes wrong I would always refer (myself) and others to review HowDoI-PreventLinkedServerIssues resource from ASPFAQ site. Also the usual practice of checking of whether its a security issue to allow the logins, if so then goto the Security page (still on Linked Server Properties). Select ' Be made using this security context '. Type a login and password that exists on the remote server....(
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Read the complete post at http://sqlserver-qa.net/blogs/tools/archive/2008/01/16/linked-server-issues.aspx