Sounds like the same thing is happening to me to. I think it might have started when they updated their internet player.
At first I thought my wireless network was acting flakey, so I just hooked up directly to the ethernet and I am still having the issue. All other internet related activities are working fine.
I do have to say it was doing the same thing on my Iphone Sling player app too.
I don't know what else to do either.
If you are still having these issue here are some articles that may help you with your issue of freezing every 5 min. Take a look at these articles make sure you are using support browser & Are meeting minuim requirements for slingbox Pro HD.
If you are meeting the requirements make sure you are hardwired the slingbox to main route/modem. Ethernet cables over 10 feet can also cause issue with freezing video and sound. It is not recommended use a switch and wifi extender slingbox was not designed for these devices and Are not supported but may work at times.
Sling Media Moderation Team