Hey Blast1, thanks for your reply.
The laptop has a Pentium M 1.86Ghz with 2GB of RAM – perfectly adequate for a 3-camera shoot in standard definition, but it can’t even play a single HDV shot.
I did some more experimenting. I rendered a minute of HDV footage to lower quality. I placed it into an HDV sequence and discovered that it would still only play at a few frames per second – with no effects, transitions, or anything. However, in the program monitor, it would play perfectly. I tried MPEG2 and H.264 with identical results.