MikeNoLastName - 12:23 am on Apr 22, 2012 (gmt 0)
Wow, just found the apparent source. It is an obscure "search engine" (I think - it's got very little text in another language). They use that exact syntax to display others' pages in a frame over top of their own search page and found one of our affected pages there. The "link" on their site includes the space and apparently is internally processed by their server and displays our page correctly within the frame, but when G collects the link verbatim and tries to follow it, it fails, producing a 404 and a crawl error report. Not sure who is in the wrong here. The search engine or Google? But I sure hope they fix it soon.