I don't really know whether this is the right place to report this bug, but then it happened in Simultan Experimental with the Release Candidate, thus here is my bug report. :)
Game just created some new industries (well done!), amongst them two Cattle Farms, that have a Textile Mill listed as customer (and the Textile Mill has the Cattle Farms listed as suppier). Of course a Textile Mill wants nothing from a Cattle Farm, thus something isn't right. My apologies if it's a known bug.
Link to screenshot: http://i.imgur.com/JrmM2sk.jpg
This is Experimental RC 11.9007 with Pak128.Britain-Ex-0.8.4
Ahh, we don't have tanneries, so we link the cattle farms to the textile mills instead. Once somebody produces some tanneries, we shall sort this out. Thank you for the report, though!