Take a look at the following links. You'll find the most common reasons for this behavior.
You can also include more details about this issue that you have; is the issue happening only remotely? Did you already test another network and computer at the remote location? How is the Slingbox connected at home? Internet speed, etc.
I have the same problem now with a newly refurbished PRO HD provided by Slingbox. I can't see past 150 kbps streaming... usually hangs around 115 kbps. Both end of the internet is well beyond specification...
Slingbox location is 9 Mbps down/ 1.92 Mbps up
Slingcatcher location is 14 Mbps down and 1.92 Mbps up
Tested via Speedtest.com.
Stop giving up generic weblinks... it is infuriating to see those pages. I personally tested that slingbox on my own network and achieved 8200 kbps streaming. Sent the box oversea and now only got 100 kbps?