Last night I was preparing to re-glue my CX tubulars (White Challenge Grifos). I deflated and removed the tires, but when reinflating one of the tires, there was a small popping sound after only a 1 or two pumps. It appears that there's now a puncture/hole near the valve stem.

I tried adding some sealant (Stan's), but it would not go into the tire.

I can't remember if I had added Stan's sealant to this tire before. If I had, I'm thinking it sealed over the valve stem opening and obstructed the inflation--resulting in a small blow out.

Has anyone experienced something like this? I'm planning to attempt getting some sealant in one more time before pulling the base tape....