I am experiencing the same problem, over the last several days, I get “Your database contains 2923 404 errors.”
For example
2012-12-12, 9:19 PM 209.239.114.234 /browse.php/Phm0gx5V/Ca81x9n9/juKOe5Db/uHdwYVcD/mHOS_2Ba/MOvKyAbA/jfInq_2F/GddfPlUm/FGurlv4L/hNyp07ai/nAvlD3YZ/oD0smfVL/b13/
2012-12-13, 11:42 AM 66.249.73.182 /shop_order_status-sitemap.xml
2012-12-15, 10:26
130.216.147.183
125.239.115.181
119.224.136.105
49.224.106.186
49.224.237.191
216.232.179.143
49.224.237.192
49.224.237.196
125.236.236.227
49.224.237.197
49.224.252.176
49.224.252.177
203.118.149.40
58.96.79.103
121.74.49.65
182.54.161.10
210.55.255.107
125.238.26.63
etc
I checked all my links and none gave 404 errors
I don’t understand what is happening.