Most CF cards have different transfer speeds depending on the quality.
If you go to the cards website, Kingston, SanDisk, Lexar, Simple, ect.
You can get a detailed CF data sheet. Some are outright slow transfering a pic from camera to memory. That would slow down your second pic, as memory is being written to the card.
Im new to CF also, just got an HP315 (One 48meg SanDisk-one 32meg Lexar)
When I was comparing the Lexar to the SanDisk, stats for the SanDisk were much faster)
Here are some of the speeds I found back then,
CF Speeds