I understand that you are not able to connect to the Slingbox right now. It's necessary to determine if you only have this trouble remotely or at the Slingbox location as well. If the issue is only remotely (at home it works), I recommend you to have a look at this article:
Let us know if this helps.
I have a Slingbox connected to a digital video recorder, which gets the TV signal from a cable box. I had a similar problem that started in December and extended into this month -- the sling viewing windows all show that streaming was occuring but the image was blank. I was finally able to determine the problem this week with a personal visit to the place where the SB is installed -- turns out that the cable box had turned off, possibly due to a large windstorm knocking out power and afterward the DVR and SB restarted normally, but the cable box did not. Once I manually turned the cable box back on, normal viewing operations resumed.
Hopefully, the cable box will stay on, but should I notice the problem again, I can at least call the building manager who has a key to my SB location to go inside and restart the cable box. It may also be possible for the cable TV service provider to issue a remote command over their coax to restart the cable box.