Str82u - 11:29 am on Jan 9, 2013 (gmt 0)
In GWT, on the "crawl error" page you can select each error and by type of error. When you check the links by clicking them, what additional information does it give you about where the links are "Linked From" (that's the name of the tab)?
Not sure what you mean, think you mean where the links comes from to those odd 404
It's likely the errors are links created by crawl mistakes but it would be interesting to know if they are all from your site or if there are any external links creating them.