Several WU's downloaded minutes apart become orphaned

One of my computers #65129 (single CPU) downloads 7 WU's over a few minutes span of time. The first 6 become orphaned, and only the last one downloaded runs. A quick check of the oldest WU's on my pending list reveals other machines doing the same thing... Dual CPU machines seem to download 8 WU's at a time. Some examples are:
#51338
#48225
#81241
#36946