Unless they've made PCI parallel port cards a lot smarter lately, I wouldn't be surprised if you need a seperate, "real" IRQ (less than 15) for each new card, or at least, have them on seperate IRQ's from each other, even if those IRQ's might be shared with some other device that will not be used concurrently.
Freeing up IRQ's: disable the onboard parallel port if you only need two ports. Also, disable any unused COM ports. Remove a LAN card to gain another IRQ.
These comments are based on battles with old WIN98, so they may be outdated with using WINXP.
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)