There is a SA 8300 thread
you should check as well as many sites on the web.
If both TVs display the same problem at the same time we can pretty much know that it is something that is shared. They share house power, coax from the splitter upstream and the CC signal.
House power--do you have other symptoms--flickering lights, dimming.
Splitter-- these usually don't go bad, unless you have it in a wet location. Splitters are cheap and the one you want will be marked with a bandwidth to 900mHz or 1000mHz. If the splitter is very old it might only be rated to about half that and should be replaced. If you ask the CC guy they will normally just give you one; many CC offices will also just give you one.
F-connectors--these little devils are often a problem. Some CC techs will just put new ones on as a matter of routine. If you decide to change them don't use twist on connectors; get ones that require a tool (crimp or compression).
The coax itself--check it for signs of damage, kinks, dents, bends less than 1.5" radius. If any part of the cable is buried or in water ensure that it is rated for burial.
Signal strength at the SA DVRs--check this several times and in wet and dry weather if you can.
Check with you immediate neighbors to see if they have the same issues with CC and if they do are they at the same time.