Take a look at the procedure described here:
forumer.com/viewtopic.php?p=9198#9198" target="_blank">http://camerahacks.10.
forumer.com/viewtopic.php?p=9198#9198
Even though it's a potentially dangerous flash write, IMO it's safer than uploading files directly to p4. So far I've only heard success stories on partition flash reads/writes to p4.
p4 seems to be at least somewhat fragmented... I believe that this is throwing off the camcorders' normal file write routines on p4. I've been meaning to try the "defrag image" option in Winimage on a p4 image to see if it improves subsequent file writes, but haven't gotten around to it.