Well, than you got a different bug than me. The problem seems to be a mis-translation of time values into the database numeric values. In my case the reason seems to be the different time/number formats that are used in the US and the rest of the world. (29.05.08 vs 05.29.08 and 1.000.000,00 vs 1,000,000.00) If I set MC to german on my (german) system and create a smartlist like "Imported the last day" the created wrong value shows up as "Imported is 31.12.1899"....which let MC to show none of my files of course. If I set MC back to english everything works as it should (These smartlists still work if I set back to german afterwards, only creating them fails) . Since you are with standard english there is something new obviously.
BTW,my bug is around since I've used the german language pack the first time...so something like 6-8 months. And its on a few very different systems with only XP pro in common...downloaded 468 right now only to verify it's still there
Perhaps one of the JRiver team should take a look. If something went wrong in this part it can cause much more trouble than our little quirks
