I have the same problem with a post which has been online for several months and suddenly disappeared for no apparent reason. In addition to the “Not Found” advisory, the following error message was generated:
WordPress database error: [Can’t create/write to file ‘C:\DOCUME~1\mysql\LOCALS~1\Temp\#sql_b8_0.MYD’ (Errcode: 17)]
SELECT DISTINCT * FROM wp_posts WHERE 1=1 AND post_date_gmt <= ‘2007-03-08 21:46:59’ AND (post_status = “publish”) AND post_status != “attachment” GROUP BY wp_posts.ID ORDER BY post_date DESC LIMIT 0, 10
Dutch Schaal’s Blog Heaven
As I said, the post was initially successful and has been residing on the site for some time.