Vista Media Center - 2 Tuners Problem with Recording

I have dual diamond extreme pvr pci/usb analog cable tv tuners installed on
my pc and have been watching and recording TV through media center. I have
vista home premium.

One thing I noticed is that when I record back-to-back shows on the same
station and have padding set to 1 min before/after, it seems that one tuner
is doing all the recording, because the second show misses the first minute.
When I used Beyond TV in the past, the second tuner would kick in and begin
recording the second show.

Does anyone know why this is happening and how to fix it?