It looks like gocomics.com changed the format of their image URLs... this breaks the regex used by grabcartoons.
At least the following comics are aaffected: adam_at_home, argyle_sweater, calvin_and_hobbes, cathy, dick_tracy, fifth_wave, foxtrot, garfield, lio, nine_to_five, non_sequitur, real_life_adventures, we_the_robots, ziggy.
The issue can be fixed by changing the regex:
FROM (argyle_sweater, specifically):
'Regex' => qr(src="(http://..uclick.com/comics/tas\/..(jpg|gif|png))),
TO (generic, seems to work for anything at gocomics):
'Regex' => qr(src="(http://imgsrv.gocomics.com/dim/\?fh=(\w{32}))),
You may need to change "src" to "href":
'Regex' => qr(href="(http://imgsrv.gocomics.com/dim/\?fh=(\w{32}))),