This has been an issue since the end of last year. It is due to slingboxes not adhering (is that spelled correctly?) to the Arqiva digital transmission specification for UK.
If you have a search you will see there are many posts about this. But Sling have NEVER responded or released corrected firmware. Now the problem is cropping up again. My slingbox pro also has the issue, freezing at about 40% tuning and then slingplayer reporting that connection to slingbox has been lost. If sling want to send me the source code I will fix it.
I have seen some posts now.
One useful one, made me pull my aerial lead out just before the tuning reaches the 'freezing' point. Put it straight back in after it goes by and it completes the search. After a few tries, you can end up with most channels if you are quick!
I think your spelling is fine and I wish I had the source code to send you.