I was seeing this until a week or two ago
We made a settings change on the new firewall to up the number simultaneous TCP connections it could handle. It wasn't the bandwidth, it was the size of the connection table in memory on the device. We were right on the edge of the old limit, and when we went over, the firewall would have to expire one TCP connection to add another, which introduced a delay. Again, that's fixed.
As far as I know, ESPN3 is still blocking us.
You didn't specify if this was with wired or wireless connections from the library. If it's wireless, that's going to persist until we get the new access points installed, which should be soon.