Update - I think all my tasks were being aborted because my Windows time was all out of whack (July 22, 2010) and all my work units were being aborted because they were deemed overdue. I would have assumed BOINC used its own time, not the local time on the client PC, but go figure. Since it won't let me grab any more tasks today (I'm over the quota since all tasks were downloaded and immediately aborted), I will find out tomorrow and hopefully everything will be working.