Generally, this issue is caused due to insufficient upload and download speed. You want to make sure you are receiving at least 1.5 mbps for both. You can check your speed at speedtest.net. Here is an article that lists the network requirements. Slingbox PRO-HD system requirements for HD and SD streaming. I hope this helps!
Sling Media Forum Moderation Team
Thanks, but this is on my home LAN, not over the internet. All connections are cabled. It is a 1Gb/s network, althought I'm not sure if the Slingbox only supports 100Mbps. In any case, bandwidth is more than sufficient.
This worked fine before the last upgrade to the browser plugin.