You need to do a better job of telling us EXACTLY what the error message says. What we are trying to tell you is that redsn0w does not pop up any error at any time which says "SHSH Blob Error". We think it must be telling you something else. You should not paraphrase error messages. Their exact text is important to help us tell you what the problem is...
There are various options for fetch, verify, submit, query, and stich, of blobs in redsn0w. Not all of this works yet AFAIK.
Run redsn0w again, and tell us at exactly that point in the process the error happens (which screen you are on in redsn0w) and exactly what the error message says. Also tell us which phone and which version of IOS you are trying to JB. Then we'll see if we can help...