According to the OC Register, Allison had a minor setback because he was pushing too hard. He tried going at 100%, but then felt the symptoms so he had to step back for a bit. He said if he were going 80% or 90%, then he'd be fine. He's still optimistic that he can return soon. He said that it could take any where from 3 weeks to 2 months, it's still a little hard to tell.
He says he "hopes to join in full-team practices by the end of next week and remains optimistic he will play soon"... so, I guess we can all take it for what it's worth. This came out of his mouth and only he knows how he feels.
Here's the article, it's at the bottom under the headline, "Allison Regresses":
http://www2.ocregister.com/ocrweb/oc...le.do?id=68831