Macro Blocking

I've got a horrible problem with macro blocking on my TV after TWC "upgraded" my cable modem. TV is an older Sony 27" XBR tube. everything was working fine, but TWC offered an upgraded modem, with seems to allow higher internet connections (i pay for the premium service, 20MB down, 1MB up). the tech came (i wasn't home), swapped the modem, and, i believe, changed the splitter. internet is fine and fast, but TV is unwatchable, and has only gotten worse over the past few days.

i've tried several different splitters, taken the splitter out altogether, rebooted the cable box (SA 8300), both by holding down the power button until the box reboots, and pulling the AC plug.

TWC can't get anybody out here until Thursday, and their phone tech support is useless. clearly the tech screwed something up, but what?

any thoughts? no rox... sux.