Thank goodness it happened today instead of during the construction of L's volunteer khakipants Tuesday night! Per "Peggy's School of Sewing Machine Repair," I'm hoping it is the bobbin case. I noticed when I changed thread colors this morning, the bobbin case didn't click in and then after stitching about 3 inches and having it jam with thread barf on the underside...WTH? My machine never does that in the middle of sewing. At the beginning if I'm not careful to make sure the thread is under the presser foot it will happen but not mid-seam. So of course, what do I do? Rethread and try again, with the same result. I think after almost 20 years of taking the bobbin case in and out, the spring would wear out eventually, even on a Viking Husqvarna. I was able to find a bobbin case and I'll be able to pick it up tomorrow morning; I can finish hemming L's shorts by hand and cut out the other pair tonight, but still - I hate the feeling of not being able to use my machine - now, today, tonight!
Update 6-6-08: It turned out to be the bobbin case after all - whew! The replacement one fit and stitched perfectly.