pci express enumeration problem

Hi,

We are using a 12 port PCI Express switch to connect 8 PCI Express cards. We are using Windows 7. The problem is when we connect the fifth card, windows keeps on loading but never starts. The fifth card has no problem as any of the four always results in proper windows start. We have already verified that all switch port are in working order

What can be the problem??

I was thinking that may be there is some enumeration issue while adding the fifth card. I want to know whether BAR space is allocated from physical memory space or system have separate address space for PCI Express?


Thanks
Ali Umair