[troyb]

You could enable the "From blocked URLs" setting in your ad blocking preferences. Then add the file giving you trouble to your blocked URLs list. OmniWeb will ignore files that match items on this list so make the items you add as general or specific as you like but keep in mind that if they're very general you may break functionality on some pages.

The blocked URLs list also uses regular expressions and requires you to format new entries to the list a certain way. So adding the urchin.js file it would look like this:

urchin\.js

Hope that helps!